create static method
创建日期
Implementation
static DateTime create(bool utc, int year,
[int month = 1,
int day = 1,
int hour = 0,
int minute = 0,
int second = 0,
int millisecond = 0,
int microsecond = 0]) =>
utc
? DateTime.utc(
year, month, day, hour, minute, second, millisecond, microsecond)
: DateTime(
year, month, day, hour, minute, second, millisecond, microsecond);