Istanbul and Tallinn Time Zone Comparison
Istanbul and Tallinn are two major cities that sit in noticeably different time zones. Istanbul and Tallinn sit on different continents, in noticeably different time zones, and at least one of them observes daylight saving time.
Because Istanbul and/or Tallinn observe daylight saving time for part of the year, the gap between them isn't fixed — it ranges between 0 and 1 hours depending on the season.
With such a small gap, scheduling a call between Istanbul and Tallinn is easy — a normal business-hours slot works for both sides on the same calendar day.