The clock is ten minutes behind.

[tzfujimino]

Hello.:-D

1. The clock/watch is ten minutes fast/slow.
2. The clock/watch is ten minutes ahead/behind.

I know #1 is correct, but I'm not sure about #2.
Does #2 work?

Thank you.

 

[Grumpy]

Yes.... and you might also hear it expressed as "The time on the clock/watch is ten minutes ahead/behind".

However, most people would say it as in your first example, ie fast/slow.