In most cases, customizers/administrators leave the Date & Time field as Local without paying much attention to detail.
With involvement of time, there are 2 behaviors while creating the field (or changing them, but there’s a catch)
You can change from Local to Time-Zone Independent any time, but can’t change from Time-Zone Independent to User Local once saved this way.
The Date & Time displayed in this field will be converted to the time-zone you are situated in.
Let’s say, the Date & Time is stored in UTC behind the scenes was 25th June 2019 6.30 PM, so whatever was stored, it will be converted to your System User’s local time according to the Settings. See below –
This type of Date & Time of field, the time is stored in UTC, regardless of where you are located in the world.
If it is 6.30 PM on 25th June in UTC, it will be 12 AM in India on 26th June
It’s pretty basic, but needs to be done carefully!
Hope this helps.