on time vs. at times

on time or at time ?

“On time” means to be punctual.

He was on time for work.

“At times” means sometimes.

She sang well at times.

  1. “At a time” means “during some moment (that is highly likely to be described).”

You have called at a bad time. - You have called during a bad period of time.
We must pull together at a (turbulent) time like this.
We have received bad news at a time when we could take no more.

  1. “At a time” means “individually or performed in individual units.”

The students came up to the stage three at a time.
We explained our behavior one at a time.
She buys skirts two at a time.
Please answer the question one at a time.

“At time” doesn’t work without some determiner.
We are accepting no new students at this time.
I would like to speak with you at some time in the near future.