This is one of only a few cases where there is a difference in preposition use between British and American English. American English uses 'on' with the word 'weekend'; British English uses 'at'. In BrE, we can use 'at weekends' or 'at the weekends' to mean weekends in general: e.g. "I never work at weekends". The phrase 'at the weekend' has two meanings. It can have the same meaning as the phrase above, referring to weekends in general, e.g. "I never work at the weekend". It can also refer to a particular weekend. For example, towards the end of the week, it's common to say to your friends, "What are you doing at the weekend?" or "See you at the weekend!" to refer to the coming weekend. [I'll leave it to American English speakers to explain how 'on' is used with 'weekend', but I just thought it was worth explaining the above before a few hundred million AmE speakers told you that 'at weekends' was wrong/weird/bad/foreign English! As is always the case, AmE speakers tend to be unfamiliar with phrasings used outside the US, while BrE speakers are very used to AmE language. In fact, I've even come across 'on' being used in British contexts of late.] I hope that helps.

In America we do not use "at weekends" just " on weekends" "on the weekend " " at the end of the weekend " You could say " at weekends end" we would just say " when the weekend was over "