Clock Time: "um"
When you want to specify an exact clock time, always use the preposition um (at).
| At six pm I finish work. | Um achtzehn Uhr habe ich Feierabend. |
(Note: *der Feierabend is a favorite word in German work culture, meaning the end of the workday or quitting time!)*
Days and Parts of the Day: "am"
For days of the week, parts of the day (like morning or evening), and specific dates, German uses am (on / in the). This is a contraction of the preposition an and the dative article dem.
| In the morning we have no time for the conference. | Am Vormittag haben wir keine Zeit für die Konferenz. |
Because a single sentence often contains both a day and a time, you will frequently see am and um working side-by-side.
| The conference starts on Monday at nine o'clock. | Die Konferenz fängt am Montag um neun Uhr an. |
| On Monday I finish work at five o'clock. | Am Montag habe ich um fünf Uhr Feierabend. |
Months and Longer Periods: "im"
For longer blocks of time—such as months, seasons, or an academic semester—use the preposition in. Just like am, this merges with the dative article dem to form the contraction im (in the).
| When is the wedding? It is in August. | Wann ist die Hochzeit? Sie ist im August. |
| During the semester we often have a lot of stress. | Im Semester haben wir oft viel Stress. |
Scheduling Vocabulary
When organizing your calendar, you will often need to arrange (vereinbaren) or postpone (verschieben) plans.
| We arrange an appointment in the morning. | Wir vereinbaren am Vormittag einen Termin. |
| Unfortunately we have to postpone the wedding. | Leider müssen wir die Hochzeit verschieben. |
Keep in mind that public holidays (der Feiertag) are treated exactly like normal days of the week, so they also take the preposition am.
| On the public holiday we do not have to work. | Am Feiertag müssen wir nicht arbeiten. |
