Timezones and Daylight Saving Time

I would like to know if UTCNOW() Function and your timezones:

automatically take into account Daylight Saving Time please?

No, UTC itself never has DST. It is the constant frame of reference other time zones are expressed relative to.

From the Wikipedia UTC page:

UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time or summer time. For example, UTC is 5 hours ahead of local time on the east coast of the United States during winter, but 4 hours ahead during summer.

In other words, when a time zone observes DST, its offset from UTC changes when there’s a DST transition, but that’s that timezone observing DST, not UTC.

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UTCNOW() gives you the DateTime value as UTC+0

So I need to identify and maintain the DST periods myself within my app?

You don’t need to identify and/or maintain any DST period. As DateTime value is read from your mobile device, your mobile or your users’ mobile devices or desktops will automatically adjust that

So technically, the Appsheet with its UTCNOW() Function is receiving the date time AND the timezone (in a mutually recognizable format) from the device?

Correct. If your device’s timezone setting is GMT+3 for example and the time clock in your device is 06/20/2019 10:45AM, UTCNOW() will the value of 06/20/2019 07:45AM. Provided your phone switches to DST, than the result of UTCNOW() will automatically be adjusted as such. Basically you can think UTC as GMT+0.