In German there are two way of expressing the time. One is formal, the other informal.

To give the time formally, you first say the hours, then the minutes. The word "Uhr" comes in between the two. In Germany, the 24-hour-clock is used to denote time.

Examples:
7.30 Uhr – sieben Uhr dreißig
20.55 Uhr – zwanzig Uhr fünfundfünfzig

The informal way of telling time is to first say the minutes, then the hours. The prepositions "vor" (before) and "nach" (after) are used to indicate the intervals between the full or half-hour marks. The 12-hour-clock is used to express the time informally.

Examples:
14.50 Uhr – zehn vor drei
15.10 Uhr – zehn nach drei