Four date meanings that must stay distinct
A UTC date-time ends in Z and describes one instant. A date-time carrying TZID describes a local clock reading in a named zone. A floating date-time carries neither Z nor TZID, so it has no fixed timezone. A DATE value is an all-day calendar date. Treating all four as ordinary browser timestamps can silently move events.
Calendar File Desk shows the original representation beside its meaning. It converts a named-zone event to UTC only when the input contains a usable VTIMEZONE definition. It does not download timezone data from an event URL or assume that your computer’s current timezone is the intended one. An unresolved zone remains visible in the report.
Review a real daylight-saving boundary
A weekly event can remain at 09:00 local time while its UTC representation changes across a daylight-saving transition. The included example keeps New York workshop times at their written local hours, skips one date, moves another instance and preserves a cancelled instance. Compare an ordinary week and a transition week before trusting a migration.
Embedded definitions are part of the source evidence. They may represent historical or customized rules, and a familiar-looking TZID is not proof that two files contain identical definitions. If selected files define the same TZID differently, the merge is withheld. Export those sources separately or correct the definitions in the originating calendar.
Do not subtract a day from the stored all-day end
An all-day event beginning on October 23 and ending on October 25 occupies October 23 and 24. The DTEND boundary is exclusive. The table and CSV retain that boundary rather than changing the event to match an informal display label. A one-day DATE event without an end has the standard one-day default.
The preview window is based on each occurrence’s original start date. It does not automatically show every ongoing multi-day event that overlaps the window, and it does not convert all-day dates into midnight UTC. Import a copy into a separate calendar, inspect the same dates, and keep the original export until you have checked the result.