A modified version of the Julian date denoted MJD denoted MJD days from the Julian date JD,
The MJD therefore gives the number of days since midnight on November 17, 1858. This date corresponds to 2400000.5 days after day 0 of the Julian calendar.MJD is still in common usage in tabulations by the U. S. Naval Observatory. Care is needed in converting to other time units, however, as a result of the half day offset (unlike the Julian date , the modified Julian date is referenced to midnight instead of noon) and because of the insertion of semiannual leap seconds (which are inserted at midnight).
The following table gives the modified Julian date for the "zeroth" of each month at 0 UT. So add
to get the Julian date of a given day D of the month at a given time 
[Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]
The MJD therefore gives the number of days since midnight on November 17, 1858. This date corresponds to 2400000.5 days after day 0 of the Julian calendar.MJD is still in common usage in tabulations by the U. S. Naval Observatory. Care is needed in converting to other time units, however, as a result of the half day offset (unlike the Julian date , the modified Julian date is referenced to midnight instead of noon) and because of the insertion of semiannual leap seconds (which are inserted at midnight).
The following table gives the modified Julian date for the "zeroth" of each month at 0 UT. So add
to get the Julian date of a given day D of the month at a given time [Ctrl+A 全部选择 提示：你可先修改部分代码，再按运行]
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