Return an optional having a Datetime with the specified year, month, day, hour, minute, second, and the optionally specified millisecond and microsecond, if those form a valid Datetime (see Datetime::isValid); otherwise return an optional without a value.
Declared in <bdlt_datetimeutil.h>
static
bsl::optional<Datetime>
fromYmdHms(
int year,
int month,
int day,
int hour,
int minute,
int second,
int millisecond = 0,
int microsecond = 0);