Brain Teaser from an Interview for a major Global Tech Company

This Brain Teaser came up in an Interview for a major Global Tech Company. Like most teasers it’s amazingly easy when you knw the method. Could you do this under pressure of an interview though?

The code is that the letter form the day of the week and the numbers are the date. So we get the following pattern:

F21 = Friday the 21st.
S23 = Sunday the 23rd.
T25 = Tuesday the 25th.
T27 = Thursday the 27th.
S29 = Saturday the 29th.
M31 = Monday the 31st.

This particular pattern avoids every other day. Therefore the next in series is W02 or Wednesday the 2nd.