Translation:My birthday is at seven o'clock in the evening.
I am not sure that the sentence is about a birthday party. If you said this in my native German, it wouldn't make any more sense than in English, so it may well be just as strange in Dutch. "Mijn verjaardag is om ... uur" is not known to Google (other than as an accidental sequence of words that is actually part of a different grammatical structure).
It appears to me that this sentence is decidedly non-standard and therefore ambiguous: It may refer to the time of birth, or to the beginning of a birthday party. Possibly to both. As the non-standard nature and ambiguity can be preserved in the translation, it should be.
There's a good explanation in the Tips and notes section under Dates/Time so I'll copy it here:
When in English you say in the morning, or at night etc., you could literally translate it to in de ochtend or in de nacht. However, Dutch has a more common and shorter way of saying it: 's ochtends or 's avonds.
The 's is short for des, which is an old Dutch word meaning van de or in de. In time it was shortened to just 's. So while in old Dutch it would be des ochtends or des nachts, we now say 's ochtends or 's nachts.
Thanks also for the nice explanation. By the way, for those who haven't noticed: The particle o' in o' clock has almost the same meaning and a very similar history (from of the). So one could think of 's nachts as translating literally to o' night, i.e. of the night. Not the natural way to say this in English, but also not too far off.
A Dutch friend of mine specifically told me that this sentence cannot refer to “My time of birth” or any equivalent. The Dutch sentence specifically means “My birthday party is at seven o’clock in the evening.”. Unfortunately, despite several reports, that was still not accepted the last time this sentence came up for me, and the currently accepted English sentence without the word “party” makes no sense at all.
I thought it was 'around' as in a moment of time that's not completely fixed. In the sense that the birthday could be a few minutes later/earlier, flexible time, an approximation. But I guess you can't use 'om' to mean that here, only when it comes to space...I think I get it now. :D
It's not a plural, it's a genitive singular. In antiquated English texts you may occasionally find phrases such as "of an evening". This Dutch construction is very similar. In German it's still obvious what's going on:
- Dutch: 's avonds.
- German: des Abends.
- Overly literal English translation: the evening's.
As you can see, Dutch has shortened the (obsolete) masculine genitive singular definite article des to 's but kept the (obsolete) genitive ending in -s. In German, all the grammatical features are still very much alive. Instead of shortening des, German speakers just drop it entirely: abends has become a one-word adverb meaning in the evening that is nowadays almost always preferred over des Abends.
The origin of this construction is probably an idiomatic phrase such as in the evening's course (in the course of the evening).