The original Greek of Revelation 22.2 reads as follows:
καὶ τοῦ ποταμοῦ ἐντεῦθεν καὶ ἐκεῖθεν ξύλον ζωῆς ποιοῦν καρποὺς δώδεκα, κατὰ μῆνα ἕκαστον ἀποδιδοῦν τὸν καρπὸν αὐτοῦ
So the key phrase is ποιοῦν καρποὺς δώδεκα, “making twelve fruits”. By itself this could mean anything. It could be 12 fruits per month as per the OP; it could be 12 fruits spread over a year; or it could be 12 fruits as an unqualified total. In this last case we would not be able to specify any particular time frame. We simply have a count of fruit and nothing else.
But of course the phrase is not by itself. The next phrase is κατὰ μῆνα ἕκαστον ἀποδιδοῦν τὸν καρπὸν αὐτοῦ, “according to each month giving its fruit.” When we put the two phrases together the likely picture is of a twelve month cycle. The fruit has the sense of harvest, and the tree will produce a harvest every month, twelve harvests a year. This would of course be in contrast to a typical orchardist’s experience of one annual crop. So in this pictorial way John is wanting us to imagine a tree that is always productive, always bearing fruit no matter the season.
For the sake of completeness it’s worth noting a second interpretive issue regarding the “twelve fruit”. The English translations are divided over two options:
- “bearing fruit twelve times.” This reading interprets “fruit” as the
generic produce of the tree, and “twelve” is the count. Thus the
fruit will be the same each month. The NIV adopts this
interpretation: “bearing twelve crops of fruit.” See also the GNB
and the NASB footnote.
- “bearing twelve kinds of fruit.” This reading interprets twelve as
applying to different categories of fruit. For instance J B Phillips
translates “bearing twelve fruits, a different kind for each month.”
See also the KJV, NASB and RSV.
Given the differences in the reputable versions, we should be cautious. But my personal view is that the first option fits better with the overall picture John is creating. He’s not pointing to different kinds of fruit. The tree in view is “the tree of life”, the tree whose fruit is life. This is a clear reference back to Genesis 2. So we have one main fruit and the number twelve is intended to emphasise the constancy of that fruit. No matter the season, the month, the time, the tree is producing its fruit of eternal life.