Every local time is Coordinated Universal Time (UTC) plus the zone's UTC offset. The converter turns the time you enter into UTC and calculates every target zone from there:
Example: Berlin in winter (UTC+1) → New York (UTC−5)
The offset comes from the IANA time zone database built into your browser. It records for every region whether and when clocks change, including past rules, so the time difference is right for any date, not just today.
Times inside the spring-forward gap (e.g. 02:30 on the last Sunday in March) are moved forward by the length of the gap. Times that occur twice in October refer to the first one, i.e. summer time.
The meeting planner checks the first location's day in 15-minute steps: a slot works if it lies completely within local working hours at every location. The current time comes from your device; no data is stored.