Timestamp of ODK Central

What timestamp standard does ODK Central server follow?
Which time is recorded as "submissionTime" when a submission is made from ODK Collect ?

In the browser, Central will display the Submission time in the time zone of the device accessing the site. If you download the data it should be in UTC as noted by the "Z" at the end of the string. I don't think there is a way to tell the "local time" from the automatic metadata. You'll likely also need to collect the location in order to determine it. Knowing/storing local time can be quite challenging. For example, when there are edge cases like Haiti cancelling daylight savings in 2016 with 2 days notice.

Zulu Time Zone is often used in aviation and the military as another name for UTC +0. The letter Z may be used as a suffix to denote a time being in the Zulu Time Zone. (source)

The two screenshots below show the same submission.
Screen Shot 2021-10-22 at 3.22.27 PM
Screen Shot 2021-10-22 at 3.23.13 PM