たことがある

たことがある says you have done something at least once in your life: "have done", "have ever". The verb is in the た-form, and the negative, たことがない, is "have never". Polite: ことがあります, ことがありません.

Not for one dated event

たことがある is about experience, not about something that happened at a known time. A recent, dated event takes the plain past.

• × 昨日、映画を見たことがある → 昨日、映画を見た

A period long past is fine, since it is still about your experience.

For the same reason, it sounds odd about something everyone does every day, like eating rice, unless there is a reason to bring it up.

たことがある or ことがある

After the dictionary form or the ない-form, ことがある is a different pattern: "there are times when", "sometimes". The た is what tells them apart.

Usage notes

These go beyond plain "have done".

は for contrast

が becomes は when you contrast: you have done it, but only that much, or this but not that.

Never even once