てからというもの（は）Ever since a significant event
てからというもの（は） looks back to an important event and presents the time since then as a noticeably different period. The later state, habit, attitude, or trend must have continued or repeatedly occurred.
A turning point with lasting consequences
The first event divides life into a before and an after. The second part describes what has characterized the period since that event—often up to the present, or up to another reference time established by context. The change may be welcome, harmful, or emotionally mixed.
Positive, negative, and mixed changes
Notice that each result is a lasting state or repeated pattern, not a single later event.
娘が生まれてからというもの、家で過ごす時間を何より大切にするようになった。
Ever since my daughter was born, I have come to value time spent at home above everything else.
Analyze弟が事故に遭ってからというもの、母は電話が鳴るたびに身構えるようになった。
Ever since my younger brother was in an accident, my mother has tensed up whenever the phone rings.
Analyzeあの失敗をしてからというもの、何かを決める前に必ず誰かに相談するようになった。
Ever since that failure, I have made a point of consulting someone before making a decision.
AnalyzeThe new caution may be beneficial, but the sentence also carries the emotional weight of the failure that caused it.
What the optional topic marker does
は is optional. Adding it makes the period beginning with the turning point more explicitly the frame for what follows; it is especially natural when the speaker is contrasting that period with earlier life.
子どもが独立してからというものは、夫婦で出かける機会が増えた。
Ever since our child became independent, my spouse and I have had more opportunities to go out together.
AnalyzeNeutral since versus a conspicuous change
て以来 can simply establish the point from which a situation has continued. てからというもの presents the same kind of timeline with a stronger sense that the event had a striking impact and that life has been different ever since. The matched sentences below describe the same habit, but the second draws attention to the change caused by joining the company.
この会社に入って以来、毎朝六時に起きて勉強している。
I have studied from six every morning since joining this company.
AnalyzeThis is a relatively neutral statement of the starting point and continued habit.
この会社に入ってからというもの、毎朝六時に起きて勉強している。
Ever since joining this company, I have been getting up at six every morning to study.
AnalyzeThis version presents joining the company as a turning point that noticeably reshaped the speaker's routine.
More examples
犬を飼い始めてからというもの、朝の散歩が一日の楽しみになった。
Ever since I started keeping a dog, the morning walk has become the highlight of my day.
Analyze詐欺に遭ってからというもの、知らない番号からの電話には出なくなった。
Ever since being scammed, I have stopped answering calls from unknown numbers.
Analyze店を任されてからというものは、休みの日でも売り上げが気になって仕方がない。
Ever since I was put in charge of the store, I have been unable to stop worrying about sales even on my days off.
Analyzeあの演奏を聴いてからというもの、彼女の音楽が頭から離れない。
Ever since hearing that performance, I have not been able to get her music out of my head.
Analyze新しい治療を始めてからというもの、以前よりよく眠れるようになった。
Ever since starting the new treatment, I have been able to sleep better than before.
Analyze