I am from Canada and planning a trip to Australia either February or March. I am sure that if I leave Winnipeg on a Thursday, I will arrive at Sydney Saturday (Sydney's time). But if I leave Syndey on Monday, will I get back to Winnipeg Monday or Tuesday (Winnipeg/Canada's time)?

Thanks!

depending on reasonable connections you will be back in winnipeg on the monday.
sydney is about 15 hrs (and 10 yrs) ahead of winnipeg time.

We left Auckland (about 3 hours closer to North America than Sydney) at 6pm on Sunday, had to change planes in LA and Dallas and still arrived home in Chicago by 10pm on Sunday. We arrived in LA before we left Auckland ! Isn't the dateline fun!?

You indeed lose a day going there - if you leave on Thursday, as you said, you get there on Saturday - Friday never happens.

But you get the day back on the return, as has been said, you leave Australia after lunch on a Monday and you get into LAX or SFO or SEA by about mid-morning that same Monday.

We left LAX at 11:20 PM 7/9 and arrived in Brisbane at 6:05 AM 7/11. When we left Sydney at 1:25 PM 7/31 and arrived in LAX at 9:45 AM 7/31.