I am wondering how accrual periods & reset dates on Quarterly-IMM swaps are different to normal swaps (in terms of conventions). For example:
PaymentDate Fixing Date Accrual Start Accrual End Accrual Factor 2019-03-05 2018-12-05 2018-12-05 2019-03-05 0.250 2019-06-05 2018-12-05 2019-03-05 2019-06-05 0.255 2019-09-05 2018-12-05 2019-06-05 2019-09-05 0.255 2019-12-05 2018-12-05 2019-09-05 2019-12-05 0.252
PaymentDate Fixing Date Accrual Start Accrual End Accrual Factor 2019-03-20 ? ? 2019-03-20 ? 2019-06-19 ? ? 2019-06-19 ? 2019-09-18 ? ? 2019-09-18 ? 2019-12-18 ? ? 2019-12-18 ?
I am asking because a normal LIBOR-3M swap has payment dates exactly 3M apart (ignoring ModFollowing, etc) and will thus produce accrual periods that are 3M long ($\rightarrow$ accrual factors of ~0.25).
IMM Swaps on the other hand may have payments dates that are a little less or more than 3M apart. Will this simply result in smaller or larger Accrual Factors (say 0.22 or 0.27)? And when does the reset/fixing happen? On the previous IMM date (= previous payment date) or just 3M prior to the current payment date? What are the conventions?