The timezone of a session should be recorded and used for import/export and display purposes
I've been using Meditation Assistant for a long time and during this time I traveled across timezones and twice a year clock is forwarded or reverse due to daylight saving. However Meditation Assistant always converts times to the current local timezone / utc offset. So, when I view meditation times whilst I was in North America instead of Europe it appears I have been meditation late in the afternoon in stead of first thing in the morning.
If the current timezone was saved with each recorded session, it can be used to translated the utc time back to the local time at the time the session was recorded in stead of the current local time. Actually I would suggest using the timezone offset to UTC (like +01:00, -09:00) so daytime saving is covered as well and no 'translation' needs to be made.
When showing the time of a session, it should always be converted to the timezone during the session. For calculating the meditation streak the current method can still be used, or one could argue you must have meditated once a day based on the local timezone (this gives you extra time when flying to the east, but less time when flying to the west).
For in- and exporting I would suggest using ISO 8601 time formats with UTC offsets like "2018-08-01T12:34:56-04:00" as they are unambiguous.