I usually work a nine hour shift sometime between 8 a.m. and 11 p.m.
My shift usually lasts about nine hours, and starts sometime after 8 in the morning and finishes by 11 at night.
ーI usually work a nine hour shift sometime between 8 a.m. and 11 p.m.
「大抵朝8時から夜11時の間で９時間のシフト勤務です」
work a nine hour shift で「９時間のシフト勤務をする」
sometime between 8 a.m. and 11 p.m で「8時～23時の間で」を表現できます。
ーMy shift usually lasts about nine hours, and starts sometime after 8 in the morning and finishes by 11 at night.
「私のシフトは通常９時間ほどで、朝8時以降、夜の11時までの間です」
to last で「時間的に続く」
starts sometime after 8 in the morning and finishes by 11 at night で「朝8時以降のどこかで始まり、夜11時までに終わる」
ご参考まで！
カナダ 
