To specify the dates on which Muslim months begin for a given Muslim Calendar Source, select a Muslim calendar, or create one, in the Calendar and Dates tab of the Muslim Data Source Manager and use the Muslim Year spinner to move to the appropriate Muslim Year.
As shown above, there are 4 columns. The first column lists the names of the Muslim months, the second column displays the dates of the beginning of the months according to the Saudi Umm al-Qora calendar. The third column displays the beginning of months dates for the selected calendar, and any change in that column is reflected in the fourth column which displays the dates of selected Muslim holidays based on the dates of the selected calendar (this is usually a good way to check your data).
You can then indicate the dates on which your calendar is in disagreement with the list generated by Q++. This is done by selecting the date and using the plus and minus buttons. You cannot move Muslim dates by more than 2 days in either direction. This makes sense since, moon phases dates differences are caused by differences in time zones, and the maximum difference in the occurrence of a moon phase between 2 time zones is 1 day. Despite this, Q++ allows for 2 days because some odd time zones differ by more than 24 hours. When you have moved a date, Q++ will highlight the new date in yellow.
The checkbox Dates for this Muslim Year are Validated is used to indicate to Q++ whether you have checked the dates for the selected calendar and year, and is used to issue warnings if you run a diary that uses a Muslim calendar on a year for which you have not validated the dates for the beginning of each month.