# `Calendrical.IncompatibleCalendarError`

Exception raised when an operation is attempted between two
dates or datetimes that use incompatible calendars.

### Fields

* `:from` — the first calendar (or value carrying it).

* `:to` — the second calendar (or value carrying it).

* `:reason` — `:day_rollover` where a date cannot be converted from one
  calendar to the other because their days begin at different times, as
  `Date.convert/2` answers, or `nil` where the two must be the same.

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*Consult [api-reference.md](api-reference.md) for complete listing*