Fill in the next logical letter-number combination in this sequence:?

[charlesdclimer]

S 30, O 31, N 30,____?

[goodwin333]

The nxt letter number may either D31 or J 31
D31 because of the month day combination
J31 because S30 O31 (OPQRS, ie decrease to O from S) N30 (decrease to N from O) then J31 (JKLMN, decrease to J from N).

[Rockmum]

no idea!!!!!!!!!!!

[Archie]

Centrelink

[SHAAN]

S 30,o 31,n 30,d 31

[M G]

S 30 O 31 N 30 D 31

Hint:
S = September
30 =number of days

[mindhunter07]

Answer is D 31
because S 30 stands for September with 30 days
O 31 stands for October with 31 days
N 30 stands for November with 30 days
which gives December with 31 days (D 31)