〜ことがある
Formation
Meaning
Indicates that something happens occasionally, even if it's not always the case.
Note
Used to describe things that happen from time to time or under certain conditions. It is almost always preceded by a verb in the non-past form (dictionary form or negative form). When preceded by a past-tense verb ([V]{ta}), it expresses experience ('have done before'), which is a different usage. It is often used with frequency adverbs like 'たまに' (occasionally), 'ときどき' (sometimes), or 'たまに〜ない' (sometimes don't).
Examples
朝ご飯を食べないことがあります。
Sometimes I don't eat breakfast.
たまに一人で山に登ることがあります。
Occasionally I climb mountains alone.
夜、なかなか寝られないことがあります。
There are times when I can't fall asleep easily at night.
この辺りは雪が降ることがありますか。
Does it ever snow in this area?
たまに日本語が分からないことがあります。
Sometimes I don't understand Japanese.
たまに自分で料理を作ることがあります。
Occasionally I cook for myself.