"on" or "at" when talking about flight dates

I originally had text on a web site that stated:

Showing flight results for flights from LON to NYC leaving at 01/06/2015 and returning at 08/06/2015

One of the testers has said that this should actually be:

Showing flight results for flights from LON to NYC leaving on 01/06/2015 and returning on 08/06/2015

which is correct?

Solution 1:

This is the first result for googling "grammar in vs on for dates": http://5minuteenglish.com/mar18.htm

You use on for dates. You use at for times. You would use in for months or years.

So in your case, the tester is correct.

"I am leaving on March 25, 2015."

"I am leaving at 12:00."

"I am coming back in April."

Solution 2:

We use the pronoun on when saying that something happens on individual days:

• on Monday
• on 4th January
• on Independence day
• on her birthday
• on Valentine's day
• on that day

We also use at for points of time in the day:

• at 5 pm
• at midnight
• at noon
• at dawn
• at lunchtime
• at zero hundred hours

The original poster need on here, because the given time is a day:

• on 01/06/2015