A: What took you so long? I've been waiting for you for ages!
B: Sorry! I missed the bus and had to walk here.
A无奈说好吧，没关系，Better late than never！
A Oh well, never mind. Better late than never！
This popular idiom is used to say that it is better to do something late than not do it at all. People often use it when someone arrives late for a meeting, but it can also be used, for example, when an email or a letter arrives late, when somoene finishes some work after the deadline has passed, or when a person finally gets around to doing something that they've been putting off for a long time.
There is another expression that has a similar structure, 'better safe than sorry'. We say this when we are being careful because something bad might happen later. For example, if it's cloudy and I take an umbrella because it might rain later, I can say 'better safe than sorry'.
我时常忘记朋友的生日，总是过了两三天才想起来，于是我在生日祝福里总要加一句“Better late than never”，意思就是“虽然晚了一点，但总比完全忘记了要好”。
另外，有一个类似的表达--“better safe than sorry”，意思是“宁愿麻烦一点做件什么事儿以防万一，总好过以后后悔当初没有采取防范措施”。阴天的时候，妈妈就经常提醒我带上雨伞，就是”better safe than sorry”。
The expression better late than never means:
a) it isn't worth doing something if it is late
b) doing something late is better than not doing it at all