Before giving my suggestions, I'd like to state two basic realities about 'datetime' of photos and videos. They are:
1. For a photo(.jpg), 'DatetimeOriginal' tag in Exif, which indicates the taking time of the photo, is a local time. The local time can not transferred to a timestamp, unless a time zone is specified.
2. For a video(.mp4 or .mov), the 'Createdate' is a UTC time. It is a specified moment.
So, if a user always lives in one timezone, the app could handle the time without any problem as I know. However, if the user travels abroad to another timezone, the photos and videos which are about to be pinned to the timeline need the real timezone information to determine the sequence.
Here are my suggestions:
1. Let user manually specifies the timezone of photos and video. For videos, the timestamp could obtained form 'Createdate', and the timezone only impacts the display datetime format. For photos, timezone is needed for determining it's timestamp.
2. Read the gps date in photos and video to determine the timezone. If gps information is lost, read the ip when a user is uploading his photos and video. This is how 'google photos' app does, but it still could cause some problems. For example, when a user comes home after a travel to a different timezone, and start to uploading photos and videos to nas. Unfortunately, some photos taken during the travel do not have gps information (but others do have). The ip is of a different timezone now when uploading. This will confuse the software and result in two timezone.
So, plz add timezone tag to Synology photos and let user to specify the timezone manually (must do). And utilize the gps information or ip address to help generate the timezone information (still recommended).
By the way, new version of Exif standard(v2.31) has already added a 'OffsetTime' tag, it could be used in the future when phone or camera makers finally use this tag. Additionally, if QuMagie colud help users write the OffsetTime back to the old photos, it will save lost of effects when users need to shift to another photo management software in the future. (I mean from QuMagie to Qumagie II
(If datetime information is missing, modified time provided by system should be use. I think Qumagie is already capable of doing that.)