Microsoft Outlook supports adjusting the Hijri date by one or two days to align the number of days in the calendar month with the moon.
For example, when an Offset value of 1 is selected in the Hijri Calendar Settings dialog box, if the current date was supposed to be Monday Ramadan 5, 1417, it will become Monday Ramadan 4, 1417, and the month of Shaaban 1417 will be made up of 30 days instead of 29.
Notes
The shifts in the Hijri calendar affect the current month, and the decision to adjust it is usually made on the first day of the month. In some cases, the effect could continue throughout the next month if the next month consists of fewer than 30 days.
Be sure to use an Offset value of zero to avoid affecting any months that do not need to be adjusted.
Appointments created during months when an Offset value has been incremented, will be shifted by one or two calendar days when you look back at them after the offset value option has been set to zero.