

昨日は夜遅くに帰りました。
夜遅くに電話しないでください。
こんなに遅くにどこへ行くの?
"おそくに(遅くに)" is in the lesson "When" (Level 42), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.