For a mixed-location group, include the full date, local time, and an unambiguous zone identifier such as Europe/Istanbul or the city and country. “Tomorrow at 10” is ambiguous near midnight and across time zones.
Use a time-zone converter for key participants, then send a calendar invitation whose time zone is set correctly. Check the meeting date in each location; conversion can shift a call to the previous or next day. For regions with daylight saving changes, an offset that works today may not work on the meeting date.
If plans change, update the invitation rather than leaving conflicting times in chat.
Akousa