～たものだ— Those Were The Days

• 子供のころ、よくこの川で泳いだものだ。

  Kodomo no koro, yoku kono kawa de oyoida mono da.

  As a child, I used to swim in this river a lot.

  泳いだ (past of 泳ぐ) + ものだ recalls a fond habitual past action

• 学生時代は、夜遅くまで友達と語り合ったものだ。

  Gakusei jidai wa, yoru osoku made tomodachi to katariatta mono da.

  In my student days, we would talk with friends late into the night.

  語り合った + ものだ expresses nostalgic recollection of a routine

• 昔はこの辺りも静かだったものだ。

  Mukashi wa kono atari mo shizuka datta mono da.

  This area used to be so quiet back in the day.

  だった + ものだ reminisces about a past state with feeling

• ・Often paired with よく ('often') and time markers like 昔 or 子供のころ.
• ・Expresses nostalgia; not just any past fact — there is emotional coloring.
• ・Register: neutral; common in reflective storytelling.

Commonly confused with

The JLPT rarely asks whether you recognise a pattern — it asks which of several similar patterns fits. These are the ones ～たものだ is tested against.

• ～一方だ — Heading Ever Further In One Direction
• ～がちだ — Prone To It
• ～からいうと／からいえば — Speaking In Terms Of
• ～からして — Even Just From
• ～かわりに — Instead Of / In Exchange
• ～きり — Only / And Never Since
• だらけ — Covered All Over
• っけ — What Was It Again?