Errors

go-bs returns errors, not panics (except MustParse, which documents that it panics). Every validation error wraps one of these sentinels.

Sentinel	Returned when
`ErrInvalidYear`	A BS year is outside `MinBSYear..MaxBSYear`.
`ErrInvalidMonth`	A BS month is not in the range 1..12.
`ErrInvalidDay`	A BS day is not a valid day of the given month — either out of the generic 1..32 bound, or greater than the actual days in that month/year.
`ErrOutOfRange`	An AD date falls outside the Gregorian range corresponding to `MinBSYear..MaxBSYear`.
`ErrInvalidFormat`	A string passed to `Parse`, `UnmarshalText` or `Scan` is not shaped like `"YYYY-MM-DD"`.
`ErrInvalidDateOrder`	`Age`'s `birthBS` is after its `todayBS`.

Checking for a specific error

Every returned error wraps one of the sentinels above via fmt.Errorf's %w verb, so use errors.Is rather than comparing strings or equality directly. The one exception is Scan given an unsupported source type (e.g. an int), which returns a plain error that wraps no sentinel.

_, err := bs.NewDate(2080, 1, 32)
if errors.Is(err, bs.ErrInvalidDay) {
	// handle specifically
}