字符串转换为时间间隔.

计算相对时间差.

判断t_ahead+delay_sec是否大于t_after，即过期.

判断t_ahead+delay_sec是否大于t_after，即过期.

IsZero reports whether t represents the zero time instant.

IsZero reports whether t represents the zero time instant.

时间戳转日期.

parseDate returns time.Date given string containing number of days since Jan 1, 1970,or zero value of time.Time if the string is empty.

parseDate returns time.Date given string containing number of days since Jan 1, 1970,or zero value of time.Time if the string is empty.

ParseInLocation parse time with location from env "TZ", if "TZ" hasn't been set then we use UTC by default.

ParseInLocation parse time with location from env "TZ", if "TZ" hasn't been set then we use UTC by default.

Duration like 1s, 500ms.