getBeforeDateTime static method
获取距离给予时间前多少天的DateTime
Implementation
static DateTime getBeforeDateTime(DateTime dateTime, int beforeDay) {
return DateTime(
dateTime.year,
dateTime.month,
dateTime.day - beforeDay,
dateTime.hour,
dateTime.minute,
dateTime.second,
dateTime.millisecond,
dateTime.microsecond
);
}