Sometimes or sometime?

Sometimes means 'not always or not often':

• We usually played football at school, but sometimes we played hockey.
• I sometimes wonder whether I should give up my job and just travel.

Sometime means 'at an unknown or undecided time in the future or the past':

• Why don't you come over and have dinner with us sometime? (at an undecided time in the future)
• I knew I had met her sometime, but I couldn't remember when.