Is 'when' necessary in this sentence or not?
This picture was taken in the day (when?) we went to Piero loti.

Thanks a lot for your help in advance!
Hyuwnook

Question

Is 'when' necessary in this sentence or not?
This picture was taken in the day (when?) we went to Piero loti.

Thanks a lot for your help in advance!
Hyuwnook

Answer

The picture was taken on the day (that/when) we went to Piero loti.

Use "on" for specific days. The "when" is not necessary.