Unit
DateUtils
DaysBetween(const ANow, AThen: TDateTime): Integer;//天
MonthsBetween(const ANow, AThen: TDateTime): Integer;//月
HoursBetween(const ANow, AThen: TDateTime): Int64;//小时
MinutesBetween(const ANow, AThen: TDateTime): Int64;//分
SecondsBetween(const ANow, AThen: TDateTime): Int64;//秒