It is well known that the day has 24 hours and many clocks only show twelve. Here lays the reason that one has to distinguish between the first 12 hours and the second. In English the abbreviations a.m. and p.m. are used to emphasize the morning hours or the evening hours. In German one uses adverbs in case it is unclear whether the morning or evening is meant. If - for instance - on person asks the other what time it is and the answer might be 10 o'clock, both probably know whether it is morning or night.
a.m.: morgens
Ich komme um 9.15
Uhr (neun Uhr fünfzehn) morgens am Bahnhof
an.
= I arrive 9.15 a.m. at the station.
Ich komme um halb
zehn Uhr morgens am Bahnhof an.*
= I arrive 9.30 a.m. at the station.
between noon and 6 p.m.: nachmittags
Sie sind um 13.15
Uhr (ein Uhr fünfzehn) nachmittags abgefahren.
= Sie sind
um viertel zwei Uhr nachmittags abgefahren.
= They left at 1:15 p.m..
after 6 p.m.: abends
Nachrichten kommen
immer um 9.15 Uhr. =
Nachrichten kommen immer um viertel zehn
Uhr abends.
= News are broadcasted at a quarter past nine in the evening.
Nachrichten kommen
immer um sieben Uhr 15 abends.
= News are broadcasted at 7:15 p.m.
after 10 p.m. : nachts**
Er kommt um 23.15
Uhr (nachts). =
Er kommt um viertel zwölf Uhr nachts.
= He comes at 11:15 p.m.
* Note! If there is an adverb the word Uhr has to be used in the sentence.
Er sagt, er komme
um halb acht.
= He says he comes at half past seven.
but
Er sagt, er komme
um halb acht Uhr morgens.
= He says he comes at half past eight in the morning.
**¡Note! Between abends and nachts there is no fixed limit. If a person is used to go to bed at nine o'clock then eleven is already night (nachts).
But if a person is used to go to bed around two in the morning then eleven o'clock is abends. You see, also in German grammar things are relative.
