因为日历上变化的月份长度，所以对于时间间隔有两个不同的标准测量单位。
There are two different standard units of measure for intervals because of the varying month lengths in calendars.
这个测量单位以年和月的数量报告两个事件之间的时间间隔。
This unit of measure reports intervals as the number of years and months between two events.
这个测量单位以天、小时、分钟、秒和毫秒报告两个事件之间的时间间隔。
This unit of measure reports intervals as the number of days, hours, minutes, seconds, and fractional seconds between two events.
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