They are able to go through the winter once they are established. I would take them out during the day for a few days putting them in a semi/protected place. Once hardened I think they will be OK. If a hard frost is predicted I would probably bring them in. Al

I agree with Al completely...

They would need a significant hardening off process, and if your Z8 is like this Z8 where the weather can be unpredictable into March, there is the chance you would need to move them someplace protected depending on the forecast for your area - which you would watch.

I've sown them late summer/Fall and left them outdoors - germination takes place then in late winter and those seedlings which have germinated outside will withstand my late winter frosts.

Morz8, indeed I did the same. I left the little pots outside throughout the winter, and they germinated outside. Then I thought I should have kept the seedlings under grow light and at warm temperature so they would have grown faster. Do you think they will grow well and hopefully bloom this year if I bring them outdoor now?

This is how they look like:
{{gwi:215446}}

If you've moved them inside under lights with heat, you now need to treat them as though they have germinated inside and not been outdoors at all. Hardening them off will be required before they can stay outside again.

I've never had them bloom first year from seed.