In Galatians 4:10. Paul rebukes the Galatians: 'you observe days and months and seasons and years'.
I had always taken these to be a reference to the Jewish calendar until a couple of years back when I read an article by Mark Nanos challenging that ("A Torah Observant Paul?"). Nanos argued that Paul was referring to the pagan calendar. I was very intrigued but not persuaded.
I have just read an argument from Justin Hardin (Wycliffe Hall, Oxford) which argues the same thing (Galatians and the Imperial Cult. Mohr Siebek, 2008) but at greater length. Hardin's position, in a nutshell (and without the argumentation), is this:
Paul's Galatian converts were ex-pagans and the imperial cult was a major part of their previous life. Indeed observing the calendar of the imperial cult was a civic duty. To abstain from participation would have seriously disrupted relationships with family, friends, business associates, club members and civic authorities.
But Paul's converts were also not converts to Judaism. Whilst the Jewish community might have recognized them as having the guest status in the synagogue of a God-fearer this status would not exempt them from the duty of observing the imperial cult. And the synagogue communities would not have recognized them as having full covenant membership (I have mixed a bit of Nanos in with Hardin here).
So the converts were in social-limbo and under considerable pressure as a result. Into this context come 'the agitators' who argue that the Galatians must fully convert to Judaism to be full members of the community of God.
The Galatians felt forced to choose between two routes to reduce the marginality of their dissonant status:
(a) convert to Judaism, or
(b) observe the calendar of the imperial cult
Some were considering the former route (and 4:21-5:6 addresses this group).
Many had already gone back to observing the events of the imperial cult (alongside their faith in Christ). They had turned to 'another gospel' (the gospel of Caesar) (1:6-7).
Paul calls them to resist both a return to pagan observances and conversion to Judaism. He points to a Third Way - a new identity in Christ and the way of the cross that accompanies it.
So 4:8-10 is an appeal to the Galatians not to go back to the observance of the imperial cult. This, he argues, would be to return to the slavery to those who are by nature not gods (i.e., the emperor-seen-as-a-deity). Do you want to be their slaves again (4:9)?
Israel, God's child, knew what it was to be a slave to pagan rulers in Egypt (an heir but unable to inherit the promises) (4:1-3) (following J.M. Scott's interpretation). God sent his Son to enable Israel to come into its inheritance by redeeming it from the curse of the Law (not from the Law itself. 4:4-5 following Todd Wilson's interpretation). You guys, says Paul, are sons and heirs along with Israel (4:6-7) so why on earth do you wish to turn back to your former pagan slave masters (4:8-10)?
There is only one Lord (Christ not Caesar)
There is only one gospel (Christ's not Caesars)
Interesting, eh? I'm still pondering it but I am inclined to accept this take on things. In part bacause it makes more sense to me than traditional readings of Galatians which see Paul as very hostile to the Jewish Law and calendar (equating it with paganism and idolatry). Whilst I can see how the text might be read that way I find it very hard to imagine Paul taking such a view. So interpretations which do not have Paul doing so have the edge.