初参加で通りがかりの者ですがこんな感じはどうですか?
In Japan people(women) can work for a part time until her(their) daughter is 3 years old, but she(they) can work for a full time after her(their) daughter's 3rd birthday.
My daughter is 3 years old 7th January, so now I'm working from 8am to 5 pm.
My daughter is 3 years old 7th January, so my working hour is getting longer. It's from 8am to 5pm.
In Japan, parents have the right to work part-time until their children turn three.
Beyond that, they are obliged to work full time.
まあ二番目の文は言わずもがな(一番目の文に意味として含まれる)ですが。
あと、
she turned 3 years old on January 7th,so my working hours
became long time and I have a 8am to 5pm job now
文章の意味は通じます。
でも、気付いた事は
so my working hours became long time
>> my working hours got longer
and I have a 8am to 5pm job now
>> and I have to work 8 to five now
でも、>1でもとさんも言ってらっしゃるように、最初の「日本では〜」の文章があるならくどくなるので、
Since my daughter turned three this month, I'm now back to working 8-17.
くらいでいいのではないかなと思いました。
ついでに、1月7日、とはっきりした日付がなくても、earlier this monthとかでもいいかな、思いました。