What does this rebus mean?

O
N
C
E
TIME

There is a barrel with no lid and some wine in it. 'This barrel of wine is more than half full,' said Curly. 'No it's not,' says Mo. 'It's less than half full.' Without any measuring implements and without removing any wine from the barrel, how can they easily determine who is correct?

Can you count the number of triangles in the given picture?

If a wheel has 54 spokes, how many spaces are there between the spokes?

What is always in front of you but can’t be seen?

There are two guys standing face to face in a room. On a wall, there is a clock. One of those is a prophet. He tells the other guy that he will be stabbed in the back in five minutes.

Shocked to hear that, the other guy stares at the clock. Just after the five minutes, he is stabbed on the back. Can you tell what happened?

If you go to the movies and you're paying, is it cheaper to take one friend to the movies twice, or two friends to the movies at the same time?

What occurs twice in a week, once in a year but never in a day?

Find The Next Number in the series:

12 13 15 17 111 113 117 119 123 ?

My location can be determined by the below rebus.
So where am i ?