How to get my iPhone calendar events back?

I've used the iPhone Mail app to access my Gmail account ever since I got my phone and since then I've written many notes and made many calendar events which were apparently synced with my Gmail account.
I've recently downloaded Outlook to access my Gmail and I deleted my Gmail account from the Mail app. As soon as I synced my Gmail with Outlook, all of my calendar events were removed and put onto Outlook.
I managed to recover all of my notes, but how to I get all of my calendar events back onto my iPhone? There are too many to add them back individually and I don't want to use Outlook as the way to look at my calendar events.

You will have to sync Outlook, just as you did gmail. Problem is - Outlook is no longer supported as it once was. It would have been FAR smarter to have left your calendar in gmail - and then seen how the future took you. If you can run several calendars at once in the iPhone calendar app, and have then designated in different colors ( as I do) you can have the best of both worlds. I want to get rid of Outlook on my desktop - but have far more important things to do right now. It's a dying program - and WHY you want to use it on your phone, beats me - unless your work requires All of you to have this.