Month aJewishMonth only contains X days in Jewish year Y
This message will usually come from the use of the EncodeJewishDate Macro function. In the Jewish calendar, many months either have 29 or 30 days depending on the year. This message occurs if you specify a Jewish month-day pair that does not exist for the Jewish year specified.
This error can occur if you try to calculate multiple dates holidays such as The Festival of Lights. This holiday starts on Kislev 25 and lasts for a total of 8 days. The incorrect way of specifying this holidays is as follows :
The reason why the above is incorrect is that the month of Kislev does not always have 30 days, so sometimes the festival ends on Tevet 3 rather than Tevet 2.
The proper way of specifying this holiday is to base each of the 8 days on Kislev 25, and then use the add days options as shown above for the 8th day of the festival.