in/of

I prefer "in".

There are dates "in" the Christian ecclesiastical (church) calendar such as Easter, Ascension, Christmas.

In Chinese tradition, the seventh month in the Chinese calendar is called the Ghost Month.

The Buddha established a day after the traditional summer retreat (the 15th day of the seventh month in the lunar calendar, usually mid-to-late August) on which Mahāmaudgalyāyana was to offer food to 500 bhikkhus. Through the merits created, Mahāmaudgalyāyana's mother gained a human birth.

Hi Contrex

I prefer "in". Does it mean 'of' is also correct?

You know a lot about Buddhist practice. Are you a Buddhist?

No. I typed "in the lunar calendar" (with the quotation marks) into Google, and found an interesting page.

http://en.wikipedia.org/wiki/Ghost_Festival

There were many other pages which suggest that, as I thought, "in" is the most common usage.

I don't think "of" is wrong, exactly, just not used very often.