# Calculate on date types **URL:** \ **Category:** Support\ **Created:** [May 15, 2015, 2:17pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345 "2015-05-15T14:17:41Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Colin](https://getodk.b-cdn.net/user_avatar/forum.getodk.org/colin/32/5636_2.png) [@Colin](https://forum.getodk.org/u/Colin)\ **Post date:** [May 15, 2015, 2:17pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/1 "2015-05-15T14:17:41Z")
Hi all, I'd like to display a field to the user: Clinic information within 12 months of clinic enrolment (between and XXX) I would the XXX to be ENRDT + 12 months. I have tried using a calculate, eg XXX = but this is a bit of a shot in the dark (esp that + 12, heh). There is probably also a cleaner way to do this (eg can I manipulate the content of an field?) Suggestions are welcome, and thanks in advance, Colin ---
**Author:** ![Mitch\_S](https://getodk.b-cdn.net/letter_avatar_proxy/v4/letter/m/3ec8ea/32.png) [@Mitch\_S](https://forum.getodk.org/u/Mitch_S)\ **Post date:** [May 15, 2015, 4:58pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/2 "2015-05-15T16:58:24Z")
There are various date-time functions available: > **[Form Logic](https://docs.getodk.org/form-logic/)** > > ODK Collect supports a wide range of dynamic form behavior. This document covers how to specify this behavior in your XLSForm definition. Form logic building blocks: Variables: Variables reference ... e.g., decimal-date(). Note, however, that there are numerous bugs/issues with date-time arithmetic and getting the logic to respect and preserve the time portion of the date-time. Carefully test to ensure that what you write actually works. > **···** > > On Fri, May 15, 2015 at 7:17 AM, wrote: > > > Hi all, > > > > I'd like to display a field to the user: > > Clinic information within 12 months of clinic enrolment (between and XXX) > > > > I would the XXX to be ENRDT + 12 months. > > > > I have tried using a calculate, eg > > XXX = > > > > but this is a bit of a shot in the dark (esp that + 12, heh). > > > > There is probably also a cleaner way to do this (eg can I manipulate the > > content of an field?) > > > > Suggestions are welcome, and thanks in advance, > > Colin > > > > ## -- > > > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to the Google Groups > > "ODK Community" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > Mitch Sundt > Software Engineer > University of Washington > [mitchellsundt@gmail.com](mailto:mitchellsundt@gmail.com) ---
**Author:** ![Colin](https://getodk.b-cdn.net/user_avatar/forum.getodk.org/colin/32/5636_2.png) [@Colin](https://forum.getodk.org/u/Colin)\ **Post date:** [May 15, 2015, 6:15pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/3 "2015-05-15T18:15:00Z")
> There are various date-time functions available: [https://opendatakit.org/help/form-design/binding/](https://opendatakit.org/help/form-design/binding/) > > e.g., decimal-date(). > > Note, however, that there are numerous bugs/issues with date-time arithmetic and getting the logic to respect and preserve the time portion of the date-time. > > Carefully test to ensure that what you write actually works. > > Hi all, > > I'd like to display a field to the user: > > Clinic information within 12 months of clinic enrolment (between and XXX) > > I would the XXX to be ENRDT + 12 months. > > I have tried using a calculate, eg > > XXX = > > but this is a bit of a shot in the dark (esp that + 12, heh). > > There is probably also a cleaner way to do this (eg can I manipulate the content of an field?) > > Suggestions are welcome, and thanks in advance, > > Colin > > -- > > -- > > Post: [opend...@googlegroups.com](mailto:opend...@googlegroups.com) > > Unsubscribe: [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > * * * > > You received this message because you are subscribed to the Google Groups "ODK Community" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > > Mitch Sundt > Software Engineer > University of Washington > [mitche...@gmail.com](mailto:mitche...@gmail.com) Durr... don't know how I missed that. Thanks Mitch > **···** > > On Friday, May 15, 2015 at 12:58:27 PM UTC-4, Mitch Sundt wrote: \> On Fri, May 15, 2015 at 7:17 AM, wrote: ---
**Author:** ![Jan\_Priebe](https://getodk.b-cdn.net/letter_avatar_proxy/v4/letter/j/c89c15/32.png) [@Jan\_Priebe](https://forum.getodk.org/u/Jan_Priebe)\ **Post date:** [June 4, 2015, 10:07am UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/4 "2015-06-04T10:07:43Z")
> There are various date-time functions available: [https://opendatakit.org/help/form-design/binding/](https://opendatakit.org/help/form-design/binding/) > > e.g., decimal-date(). > > Note, however, that there are numerous bugs/issues with date-time arithmetic and getting the logic to respect and preserve the time portion of the date-time. > > Carefully test to ensure that what you write actually works. > > Hi, I'm trying to write a simple formula to check whether occurs a date X occurs at least 3 months after date Y, and if not, return a warning message. To do this I have created a note that only shows when this condition is not met. I have tried this using an XLSForm that is then uploaded to KoboToolbox Relevant field: decimal-date(${dateX}) - decimal-date(${dateY}) \> '90' I have also tried putting the constraint directly in the XML file to upload to ODK aggregate: " decimal-date(dateX) - decimal-date(dateY) \> '90'" in both cases I receive the error: " XPath evaluation: cannot handle function 'decimal-date' " This sounds like decimal-date isn't accepted at all as a function, though the previous post suggest it is/should be. Would appreciate any thoughts on this Thanks Jan > **···** > > On Friday, May 15, 2015 at 5:58:27 PM UTC+1, Mitch Sundt wrote: > > > On Fri, May 15, 2015 at 7:17 AM, [colind...@gmail.com](mailto:colind...@gmail.com) wrote: > > Hi all, > > > > I'd like to display a field to the user: > > > > Clinic information within 12 months of clinic enrolment (between and XXX) > > > > I would the XXX to be ENRDT + 12 months. > > > > I have tried using a calculate, eg > > > > XXX = > > > > but this is a bit of a shot in the dark (esp that + 12, heh). > > > > There is probably also a cleaner way to do this (eg can I manipulate the content of an field?) > > > > Suggestions are welcome, and thanks in advance, > > > > Colin > > > > -- > > > > -- > > > > Post: [opend...@googlegroups.com](mailto:opend...@googlegroups.com) > > > > Unsubscribe: [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com) > > > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to the Google Groups "ODK Community" group. > > > > To unsubscribe from this group and stop receiving emails from it, send an email to [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com). > > > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > -- > > > > Mitch Sundt > > Software Engineer > > University of Washington > > [mitche...@gmail.com](mailto:mitche...@gmail.com) ---
**Author:** ![Colin](https://getodk.b-cdn.net/user_avatar/forum.getodk.org/colin/32/5636_2.png) [@Colin](https://forum.getodk.org/u/Colin)\ **Post date:** [June 4, 2015, 5:41pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/5 "2015-06-04T17:41:13Z")
I was also unable to get decimal-date to work correctly. However, I believe I have an approach that could work for your issue... you can perform basic math functions on date objects in ODK. That is, you can use div, -, etc (as well as \> and \<). Snippet of my code: constraint = ( (((. - /data/ENROLDT) div 365.25) \>= 1) So, extrapolating from that, you might try something like: ((${dateX} - ${dateY}) div 365.25) \> 1/4 Or, more human readably ((${dateX} - ${dateY}) div 30) \> 3 > **···** > > On Thursday, June 4, 2015 at 1:13:46 PM UTC-4, jan.p...@gmail.com wrote: \> On Friday, May 15, 2015 at 5:58:27 PM UTC+1, Mitch Sundt wrote: \> \> There are various date-time functions available: https://opendatakit.org/help/form-design/binding/ \> \> \> \> e.g., decimal-date(). \> \> \> \> Note, however, that there are numerous bugs/issues with date-time arithmetic and getting the logic to respect and preserve the time portion of the date-time. \> \> \> \> Carefully test to ensure that what you write actually works. \> \> \> \> Hi, \> \> I'm trying to write a simple formula to check whether occurs a date X occurs at least 3 months after date Y, and if not, return a warning message. \> \> To do this I have created a note that only shows when this condition is not met. \> \> I have tried this using an XLSForm that is then uploaded to KoboToolbox \> \> Relevant field: decimal-date(${dateX}) - decimal-date(${dateY}) \> '90' \> \> I have also tried putting the constraint directly in the XML file to upload to ODK aggregate: \> \> " decimal-date(dateX) - decimal-date(dateY) \> '90'" \> \> in both cases I receive the error: " XPath evaluation: cannot handle function 'decimal-date' " \> \> This sounds like decimal-date isn't accepted at all as a function, though the previous post suggest it is/should be. \> \> Would appreciate any thoughts on this \> \> Thanks \> \> Jan \> \> \> \> \> \> \> \> \> \> \> \> \> \> \> \> \> \> On Fri, May 15, 2015 at 7:17 AM, wrote: \> \> Hi all, \> \> \> \> \> \> \> \> I'd like to display a field to the user: \> \> \> \> Clinic information within 12 months of clinic enrolment (between and XXX) \> \> \> \> \> \> \> \> I would the XXX to be ENRDT + 12 months. \> \> \> \> \> \> \> \> \> \> \> \> I have tried using a calculate, eg \> \> \> \> XXX = \> \> \> \> \> \> \> \> \> \> \> \> but this is a bit of a shot in the dark (esp that + 12, heh). \> \> \> \> \> \> \> \> There is probably also a cleaner way to do this (eg can I manipulate the content of an field?) \> \> \> \> \> \> \> \> Suggestions are welcome, and thanks in advance, \> \> \> \> Colin \> \> \> \> \> \> \> \> -- \> \> \> \> -- \> \> \> \> Post: opend...@googlegroups.com \> \> \> \> Unsubscribe: opendatakit...@googlegroups.com \> \> \> \> Options: http://groups.google.com/group/opendatakit?hl=en \> \> \> \> \> \> \> \> --- \> \> \> \> You received this message because you are subscribed to the Google Groups "ODK Community" group. \> \> \> \> To unsubscribe from this group and stop receiving emails from it, send an email to opendatakit...@googlegroups.com. \> \> \> \> For more options, visit https://groups.google.com/d/optout. \> \> \> \> \> \> \> \> \> \> -- \> \> \> \> Mitch Sundt \> \> Software Engineer \> \> University of Washington \> \> mitche...@gmail.com ---
**Author:** ![Mitch\_S](https://getodk.b-cdn.net/letter_avatar_proxy/v4/letter/m/3ec8ea/32.png) [@Mitch\_S](https://forum.getodk.org/u/Mitch_S)\ **Post date:** [June 4, 2015, 9:44pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/6 "2015-06-04T21:44:38Z")
Oops. My mistake. The name of the function is: decimal-date-time() there is no decimal-date() function. > **···** > > On Thu, Jun 4, 2015 at 10:41 AM, wrote: > > > I was also unable to get decimal-date to work correctly. > > > > However, I believe I have an approach that could work for your issue... > > you can perform basic math functions on date objects in ODK. That is, you > > can use div, -, etc (as well as \> and \<). > > > > Snippet of my code: > > constraint = ( (((. - /data/ENROLDT) div 365.25) \>= 1) > > > > So, extrapolating from that, you might try something like: > > ((${dateX} - ${dateY}) div 365.25) \> 1/4 > > Or, more human readably > > ((${dateX} - ${dateY}) div 30) \> 3 > > > > On Thursday, June 4, 2015 at 1:13:46 PM UTC-4, [jan.p...@gmail.com](mailto:jan.p...@gmail.com) wrote: > > > > > On Friday, May 15, 2015 at 5:58:27 PM UTC+1, Mitch Sundt wrote: > > > > > > > There are various date-time functions available: > > > > [https://opendatakit.org/help/form-design/binding/](https://opendatakit.org/help/form-design/binding/) > > > > > > > > e.g., decimal-date(). > > > > > > > > Note, however, that there are numerous bugs/issues with date-time > > > > arithmetic and getting the logic to respect and preserve the time portion > > > > of the date-time. > > > > > > > > Carefully test to ensure that what you write actually works. > > > > > > > > Hi, > > > > > > I'm trying to write a simple formula to check whether occurs a date X > > > occurs at least 3 months after date Y, and if not, return a warning message. > > > > > > To do this I have created a note that only shows when this condition is > > > not met. > > > > > > I have tried this using an XLSForm that is then uploaded to KoboToolbox > > > > > > Relevant field: decimal-date(${dateX}) - decimal-date(${dateY}) \> '90' > > > > > > I have also tried putting the constraint directly in the XML file to > > > upload to ODK aggregate: > > > > > > " decimal-date(dateX) - decimal-date(dateY) \> '90'" > > > > > > in both cases I receive the error: " XPath evaluation: cannot handle > > > function 'decimal-date' " > > > > > > This sounds like decimal-date isn't accepted at all as a function, > > > though the previous post suggest it is/should be. > > > > > > Would appreciate any thoughts on this > > > > > > Thanks > > > > > > Jan > > > > > > > On Fri, May 15, 2015 at 7:17 AM, [colind...@gmail.com](mailto:colind...@gmail.com) wrote: > > > > Hi all, > > > > > > > > I'd like to display a field to the user: > > > > > > > > Clinic information within 12 months of clinic enrolment (between > > > > and XXX) > > > > > > > > I would the XXX to be ENRDT + 12 months. > > > > > > > > I have tried using a calculate, eg > > > > > > > > XXX = > > > > > > > > but this is a bit of a shot in the dark (esp that + 12, heh). > > > > > > > > There is probably also a cleaner way to do this (eg can I manipulate > > > > the content of an field?) > > > > > > > > Suggestions are welcome, and thanks in advance, > > > > > > > > Colin > > > > > > > > -- > > > > > > > > -- > > > > > > > > Post: [opend...@googlegroups.com](mailto:opend...@googlegroups.com) > > > > > > > > Unsubscribe: [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com) > > > > > > > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > > > > > * * * > > > > > > > > You received this message because you are subscribed to the Google > > > > Groups "ODK Community" group. > > > > > > > > To unsubscribe from this group and stop receiving emails from it, send > > > > an email to [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com). > > > > > > > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > > > > > -- > > > > > > > > Mitch Sundt > > > > Software Engineer > > > > University of Washington > > > > [mitche...@gmail.com](mailto:mitche...@gmail.com) > > > > ## -- > > > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to the Google Groups > > "ODK Community" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > Mitch Sundt > Software Engineer > University of Washington > [mitchellsundt@gmail.com](mailto:mitchellsundt@gmail.com) ---
**Author:** ![Jan\_Priebe](https://getodk.b-cdn.net/letter_avatar_proxy/v4/letter/j/c89c15/32.png) [@Jan\_Priebe](https://forum.getodk.org/u/Jan_Priebe)\ **Post date:** [June 5, 2015, 9:06am UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/7 "2015-06-05T09:06:09Z")
Thanks both! Mitch, no worries- I really should have just tried that myself. Colin, thanks for the tip, I didn’t realise I could use dates in math functions without having to convert them first – problem solved! > **···** > > From: opendatakit@googlegroups.com [mailto:opendatakit@googlegroups.com] On Behalf Of Mitch Sundt Sent: 04 June 2015 22:45 To: ODK Community Subject: Re: [ODK Community] Calculate on date types > > Oops. My mistake. > > The name of the function is: > > decimal-date-time() > > there is no decimal-date() function. > > On Thu, Jun 4, 2015 at 10:41 AM, [colindmccann@gmail.com](mailto:colindmccann@gmail.com) wrote: > > I was also unable to get decimal-date to work correctly. > > However, I believe I have an approach that could work for your issue... you can perform basic math functions on date objects in ODK. That is, you can use div, -, etc (as well as \> and \<). > > Snippet of my code: > constraint = ( (((. - /data/ENROLDT) div 365.25) \>= 1) > > So, extrapolating from that, you might try something like: > ((${dateX} - ${dateY}) div 365.25) \> 1/4 > Or, more human readably > ((${dateX} - ${dateY}) div 30) \> 3 > > On Thursday, June 4, 2015 at 1:13:46 PM UTC-4, [jan.p...@gmail.com](mailto:jan.p...@gmail.com) wrote: > > > On Friday, May 15, 2015 at 5:58:27 PM UTC+1, Mitch Sundt wrote: > > > > > There are various date-time functions available: [https://opendatakit.org/help/form-design/binding/](https://opendatakit.org/help/form-design/binding/) > > > > > > e.g., decimal-date(). > > > > > > Note, however, that there are numerous bugs/issues with date-time arithmetic and getting the logic to respect and preserve the time portion of the date-time. > > > > > > Carefully test to ensure that what you write actually works. > > > > > > Hi, > > > > I'm trying to write a simple formula to check whether occurs a date X occurs at least 3 months after date Y, and if not, return a warning message. > > > > To do this I have created a note that only shows when this condition is not met. > > > > I have tried this using an XLSForm that is then uploaded to KoboToolbox > > > > Relevant field: decimal-date(${dateX}) - decimal-date(${dateY}) \> '90' > > > > I have also tried putting the constraint directly in the XML file to upload to ODK aggregate: > > > > " decimal-date(dateX) - decimal-date(dateY) \> '90'" > > > > in both cases I receive the error: " XPath evaluation: cannot handle function 'decimal-date' " > > > > This sounds like decimal-date isn't accepted at all as a function, though the previous post suggest it is/should be. > > > > Would appreciate any thoughts on this > > > > Thanks > > > > Jan > > > > > On Fri, May 15, 2015 at 7:17 AM, [colind...@gmail.com](mailto:colind...@gmail.com) wrote: > > > Hi all, > > > > > > I'd like to display a field to the user: > > > > > > Clinic information within 12 months of clinic enrolment (between and XXX) > > > > > > I would the XXX to be ENRDT + 12 months. > > > > > > I have tried using a calculate, eg > > > > > > XXX = > > > > > > but this is a bit of a shot in the dark (esp that + 12, heh). > > > > > > There is probably also a cleaner way to do this (eg can I manipulate the content of an field?) > > > > > > Suggestions are welcome, and thanks in advance, > > > > > > Colin > > > > > > -- > > > > > > -- > > > > > > Post: [opend...@googlegroups.com](mailto:opend...@googlegroups.com) > > > > > > Unsubscribe: [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com) > > > > > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > > > * * * > > > > > > You received this message because you are subscribed to the Google Groups "ODK Community" group. > > > > > > To unsubscribe from this group and stop receiving emails from it, send an email to [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com). > > > > > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > > > -- > > > > > > Mitch Sundt > > > Software Engineer > > > University of Washington > > > [mitche...@gmail.com](mailto:mitche...@gmail.com) > > ## -- > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) [mailto:opendatakit%2Bunsubscribe@googlegroups.com](mailto:opendatakit%2Bunsubscribe@googlegroups.com) > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > * * * > > You received this message because you are subscribed to the Google Groups "ODK Community" group. > To unsubscribe from this group and stop receiving emails from it, send an email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) [mailto:opendatakit%2Bunsubscribe@googlegroups.com](mailto:opendatakit%2Bunsubscribe@googlegroups.com) . > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > > Mitch Sundt > Software Engineer > University of Washington > [mitchellsundt@gmail.com](mailto:mitchellsundt@gmail.com) > > ## -- > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > * * * > > You received this message because you are subscribed to a topic in the Google Groups "ODK Community" group. > To unsubscribe from this topic, visit [https://groups.google.com/d/topic/opendatakit/zwwIJ6oj0n0/unsubscribe](https://groups.google.com/d/topic/opendatakit/zwwIJ6oj0n0/unsubscribe). > To unsubscribe from this group and all its topics, send an email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). ---
**Author:** ![Mitch\_S](https://getodk.b-cdn.net/letter_avatar_proxy/v4/letter/m/3ec8ea/32.png) [@Mitch\_S](https://forum.getodk.org/u/Mitch_S)\ **Post date:** [June 5, 2015, 6:32pm UTC](https://forum.getodk.org/t/calculate-on-date-types/4345/8 "2015-06-05T18:32:00Z")
There is a lot of quirky behavior around dates, so be sure to test both the success and error conditions to ensure that your form logic is actually working. > **···** > > On Fri, Jun 5, 2015 at 2:06 AM, Jan Priebe wrote: > > > Thanks both! > > > > Mitch, no worries- I really should have just tried that myself. > > > > Colin, thanks for the tip, I didn’t realise I could use dates in math > > functions without having to convert them first – problem solved! > > > > _From:_ [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) [[mailto:opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com)] > > \*On Behalf Of \*Mitch Sundt > > _Sent:_ 04 June 2015 22:45 > > _To:_ ODK Community > > _Subject:_ Re: [ODK Community] Calculate on date types > > > > Oops. My mistake. > > > > The name of the function is: > > > > decimal-date-time() > > > > there is no decimal-date() function. > > > > On Thu, Jun 4, 2015 at 10:41 AM, [colindmccann@gmail.com](mailto:colindmccann@gmail.com) wrote: > > > > I was also unable to get decimal-date to work correctly. > > > > However, I believe I have an approach that could work for your issue... > > you can perform basic math functions on date objects in ODK. That is, you > > can use div, -, etc (as well as \> and \<). > > > > Snippet of my code: > > constraint = ( (((. - /data/ENROLDT) div 365.25) \>= 1) > > > > So, extrapolating from that, you might try something like: > > ((${dateX} - ${dateY}) div 365.25) \> 1/4 > > Or, more human readably > > ((${dateX} - ${dateY}) div 30) \> 3 > > > > On Thursday, June 4, 2015 at 1:13:46 PM UTC-4, [jan.p...@gmail.com](mailto:jan.p...@gmail.com) wrote: > > > > > On Friday, May 15, 2015 at 5:58:27 PM UTC+1, Mitch Sundt wrote: > > > > > > > There are various date-time functions available: > > > > [https://opendatakit.org/help/form-design/binding/](https://opendatakit.org/help/form-design/binding/) > > > > > > > > e.g., decimal-date(). > > > > > > > > Note, however, that there are numerous bugs/issues with date-time > > > > arithmetic and getting the logic to respect and preserve the time portion > > > > of the date-time. > > > > > > > > Carefully test to ensure that what you write actually works. > > > > > > > > Hi, > > > > > > I'm trying to write a simple formula to check whether occurs a date X > > > occurs at least 3 months after date Y, and if not, return a warning message. > > > > > > To do this I have created a note that only shows when this condition is > > > not met. > > > > > > I have tried this using an XLSForm that is then uploaded to KoboToolbox > > > > > > Relevant field: decimal-date(${dateX}) - decimal-date(${dateY}) \> '90' > > > > > > I have also tried putting the constraint directly in the XML file to > > > upload to ODK aggregate: > > > > > > " decimal-date(dateX) - decimal-date(dateY) \> '90'" > > > > > > in both cases I receive the error: " XPath evaluation: cannot handle > > > function 'decimal-date' " > > > > > > This sounds like decimal-date isn't accepted at all as a function, > > > though the previous post suggest it is/should be. > > > > > > Would appreciate any thoughts on this > > > > > > Thanks > > > > > > Jan > > > > > > > On Fri, May 15, 2015 at 7:17 AM, [colind...@gmail.com](mailto:colind...@gmail.com) wrote: > > > > Hi all, > > > > > > > > I'd like to display a field to the user: > > > > > > > > Clinic information within 12 months of clinic enrolment (between > > > > and XXX) > > > > > > > > I would the XXX to be ENRDT + 12 months. > > > > > > > > I have tried using a calculate, eg > > > > > > > > XXX = > > > > > > > > but this is a bit of a shot in the dark (esp that + 12, heh). > > > > > > > > There is probably also a cleaner way to do this (eg can I manipulate > > > > the content of an field?) > > > > > > > > Suggestions are welcome, and thanks in advance, > > > > > > > > Colin > > > > > > > > -- > > > > > > > > -- > > > > > > > > Post: [opend...@googlegroups.com](mailto:opend...@googlegroups.com) > > > > > > > > Unsubscribe: [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com) > > > > > > > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > > > > > * * * > > > > > > > > You received this message because you are subscribed to the Google > > > > Groups "ODK Community" group. > > > > > > > > To unsubscribe from this group and stop receiving emails from it, send > > > > an email to [opendatakit...@googlegroups.com](mailto:opendatakit...@googlegroups.com). > > > > > > > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > > > > > -- > > > > > > > > Mitch Sundt > > > > Software Engineer > > > > University of Washington > > > > [mitche...@gmail.com](mailto:mitche...@gmail.com) > > > > ## -- > > > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to the Google Groups > > "ODK Community" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > -- > > > > Mitch Sundt > > Software Engineer > > University of Washington > > [mitchellsundt@gmail.com](mailto:mitchellsundt@gmail.com) > > > > ## -- > > > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to a topic in the > > Google Groups "ODK Community" group. > > To unsubscribe from this topic, visit > > [https://groups.google.com/d/topic/opendatakit/zwwIJ6oj0n0/unsubscribe](https://groups.google.com/d/topic/opendatakit/zwwIJ6oj0n0/unsubscribe). > > To unsubscribe from this group and all its topics, send an email to > > [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > > > ## -- > > > > Post: [opendatakit@googlegroups.com](mailto:opendatakit@googlegroups.com) > > Unsubscribe: [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com) > > Options: [http://groups.google.com/group/opendatakit?hl=en](http://groups.google.com/group/opendatakit?hl=en) > > > > * * * > > > > You received this message because you are subscribed to the Google Groups > > "ODK Community" group. > > To unsubscribe from this group and stop receiving emails from it, send an > > email to [opendatakit+unsubscribe@googlegroups.com](mailto:opendatakit+unsubscribe@googlegroups.com). > > For more options, visit [https://groups.google.com/d/optout](https://groups.google.com/d/optout). > > -- > Mitch Sundt > Software Engineer > University of Washington > [mitchellsundt@gmail.com](mailto:mitchellsundt@gmail.com)