- "We had been dating for ◯ years in this photo."
"we had been dating for ~" 「付き合って〜」"we had been together for ~" も言えます。
"◯ years" 「◯年」
"in this photo" 「この写真」
This photo was taken in the fourth year after we started dating.
ーThis photo was taken in the fourth year after we started dating.
「この写真は付き合い始めて4年目に撮られた」
in the ○ year after we started dating で「付き合い始めて○年目」
例:
When I compare this with a photo taken four years after we got married, it's quite amusing.
「この写真を結婚して4年目に撮られた写真と比べると、面白い」
ご参考まで!