I wrote: It is 14:15, but this was wrong. In English you can say it is 15 minutes past two and mean either 14:15 or 02:15, is there always a specifier in Dutch as to day / night?
The goal of this course is to teach a language, writing 14:15 doesn't teach anything, so is not accepted. Whether day or night is meant is usually clear from context, otherwise you can add 's nachts or 's middags (for 12 through 5), 's morgens/'s ochtends or 's avonds (for 6 through 11).
In writing either the 24-hour notation is used like your example, or it's the same as in speech: tien voor half 7 's avonds (ten to half past 6 PM = 18:20), with 's avonds often not included. An equivalent to AM/PM is not used normally.
Thank you for the reply, it was very helpful. I write it numerically only as it is being answered in my native language and larger numbers (or time) are often written as numerals. I see now from reading the time aloud as 15 minutes past two, it does sound better and more conversational while also being more equatable to the original sentence. The course has improved my English spelling, so it is a good reason not to cheat :D.
Well you got the time right but it's not something we'd normally say :) When telling someone the time you could say "het is 14 uur 15" but I would only use that when reading the exact time from a clock or watch, and even then when it's a "round" number like this I'd say "het is kwart over twee".
Day or night is either context (when does the swimming pool open? 10 o'clock? this would obviously be morning unless stated otherwise) or you could use "'s nachts / 's ochtends / 's middags / 's avonds" for during the night/morning/afternoon/evening, e.g. "2 uur 's nachts (2AM), 8 uur 's ochtends (8AM), 1 uur 's middags (1PM), 7 uur 's avonds (7PM)"
"kwart" means 1/4th, kwartier only means "1/4th of an hour". We use the shortened version for "quarter to" and "quarter past", the longer for speaking about "15 minutes" in general.
"Ik zal er over een kwartier zijn" (I'll be there in 15 minutes)
"Ik zal er om kwart over twee zijn" (I'll be there at 2:15)
Kwart is also not necessarily related to time, for example "Ik neem een kwart van de taart" (I take one quarter of the pie)
It seems kwartier is also used for quarter of a year. Is this correct? If I am a suit-wearing guy saying for example "het resultaat eerste kwartier 2018 is blabla duizend €"
No, that's not correct, you're close though =) A quarter or a year is called a "kwartaal" e.g. "Apple maakt resultaten derde kwartaal bekend". Related to that are the so-called "kwartaalcijfers".
Yes I would also guess on kwartaal, it is much closer to the scandinavian and German words. "Kwartier" is just another example where Google translate fails, it seems ;)