Does the time difference between Manila and Toronto change during the year?

Yes. Because of daylight saving time the gap moves between +12h and +13h.

When is the best time to call Toronto from Manila?

There is no overlap between standard working days, so one side has to call early or late.

Manila is 12h ahead of Toronto. This gap is not fixed: daylight saving time moves it between +12h and +13h during the year.

Manila

Philippines

--:--:--

Toronto

Canada

--:--:--

A 9-to-5 working day in Manila does not overlap one in Toronto at all — somebody has to take the call outside office hours.

City	Time zone	UTC offset
Manila · Philippines	Asia/Manila	UTC+8
Toronto · Canada	America/Toronto	UTC−4

What is the time difference between Manila and Toronto?: Manila is 12h ahead of Toronto. This gap is not fixed: daylight saving time moves it between +12h and +13h during the year.
Does the time difference between Manila and Toronto change during the year?: Yes. Because of daylight saving time the gap moves between +12h and +13h.
When is the best time to call Toronto from Manila?: There is no overlap between standard working days, so one side has to call early or late.