timetable

[JaneEyre]

My DS missed school recently and wasn't there when the teacher explained how to read timetables... So he is now surprised by a detail in his homework, because both of us don't know the meaning of the letters SO and SX at the top of two columns of a train timetable.

Does anybody know the meaning of these two letters?

I try to be more precise:
two trains are departing at the same time: 0520. So there are the name of all the station where both of them stop and their departure time... But one column has SO at the top, the other has SX at the top.

Curiously, they both stop at the same stations (but the departure time from one station is omitted for one train, but it still arrives at the same time as the other train at the next station).
Well, frankly, I don't know why there are two columns with the same times for two different trains! Sorry, if it seems stupid... They could have added wagons to one train!

Being more and more confused

[tiredmum]

SX - mondays to fridays
SO - saturdays only

Some timetable have a key showing this

[First-timer]

Think it might be Saturdays Only and Saturdays eXcepted. S could refer to Sundays instead of Saturdays, though.

[hermanmunster]

usually saturday rather than sunday as there is often a separate sunday timetable

[JaneEyre]

a BIG thank you to all your replies