While definite time expressions (like "every year" or "this morning") use the accusative case, German uses the genitive case to express indefinite time ("one day") and to build elegant, fixed phrases describing manner or perspective.
Indefinite Time
To say "one day" or "some day," use the masculine genitive phrase eines Tages.
| One day, we will have risked emigration. | Eines Tages werden wir die Auswanderung gewagt haben. |
Curiously, even though Nacht (night) is feminine, it copied the masculine and neuter pattern over time to create the highly common fixed phrase eines Nachts (one night).
| One night, we set out in order to risk a new beginning. | Eines Nachts sind wir aufgebrochen, um den Neuanfang zu wagen. |
Manner and Outcomes
The genitive is extensively used to form fixed expressions of manner. These phrases usually consist of an adjective ending in -en and a noun ending in -s, and they drop right into a sentence just like a normal adverb.
Common examples include schweren Herzens (with a heavy heart) and letzten Endes (ultimately / in the end).
| With a heavy heart we left the homeland behind, so we became homeless. | Schweren Herzens haben wir die Heimat zurückgelassen, sodass wir heimatlos geworden sind. |
| The farewell was sad, so we ultimately cried. | Der Abschied war traurig, sodass wir letzten Endes geweint haben. |
Similarly, to say someone is acting "in good conscience," use the fixed genitive phrase guten Gewissens.
| Should they set out, they will do so with a clear conscience. | Sollten sie aufbrechen, tun sie es guten Gewissens. |
Opinions and Attitudes
You can state your perspective using possessives combined with genitive endings. Meines Erachtens is a formal, common way to say "in my opinion" (literally: of my considering).
| In my opinion, the crossing is uncertain. | Meines Erachtens ist die Überfahrt ungewiss. |
Other common genitive phrases describe someone's attitude or mindset. Allen Ernstes means "in all seriousness," while frohen Mutes means "in good spirits."
| Did he in all seriousness leave the family behind before the crossing? | Hat er die Familie allen Ernstes vor der Überfahrt zurückgelassen? |
| On the one hand the future is uncertain, on the other hand we set out in good spirits. | Einerseits ist die Zukunft ungewiss, andererseits brechen wir frohen Mutes auf. |
Finally, just like meines Erachtens, you can use the expression meines Wissens to say "to my knowledge."
| To my knowledge, the emigration was a new beginning. | Meines Wissens war die Auswanderung ein Neuanfang. |
