GSM are not flying to YVR in the winter, so not sure what your asking.
The Summer 2008 Schedule for GSM to Wester Canada is as follows.
Monday.
DUB-YYC-YVR-YYC-LGW
Tuesday
LGW-YYC-YVR-YYC-GLA
Wednesday
GLA-YYC-YVR
Thursday
YVR-YYC-MAN
Friday
MAN-YYC-YVR-YYC-GLA
Saturday
GLA-YYC-YVR-YYC-LGW
Sunday
LGW-YYC-YVR-YYC-DUB
Not sure what there doing with the wednesday/thursday overnight in Vancouver.