'In the blink of an eye' is not particularly colloquial. I immediately thought of the Bible passage (1 Corinthians 15:52) in which the King James version and others use the expression 'in the twinkling of an eye', and more modern versions use 'blink'.
idioms - Synonym for "in the blink of an eye" - English Language ...
In the blink on an eye implies something happens in an instant, such as a sudden, unforeseen calamity. Hence, I have no problem with " Time flew during my first year at university," but it's hard to resolve a one-year event happening in the blink of an eye. So, I would suggest: Time flew during my first year at the university.
In the blink of an eye - English Language & Usage Stack Exchange
About the Bible verse I found this: 'This is translated from the Greek phrase en rhipē opthalmou, which most literally means "flicking the eye" and was the ancient reference to "the blink of an eye'. Interesting that most modern versions have kept twinkling rather than blink, despite the rather different connotations of 'a twinkle in the eye'.
Earliest printed record of the phrase "in the blink of an eye"?
4 The phrase “wouldn't blink twice” sounds to me like a conflation of a “wouldn't blink” idiom with a “wouldn't think twice” idiom. “Wouldn't blink”, in forms like “wouldn't blink an eye” and “wouldn't bat an eye/eyelash/eyelid ” connote not reacting or responding, ie, failing to show surprise.
@Jimi: Using Google, I can find blinking of an eye (as quickly) dating back to 1823 but blink of an eye only back to 1874. Blink is much more common now, but I think blinking predates it.