zu Lebzeiten
during one's lifetime
A fixed expression meaning that something happens while a person is still alive.
Schon zu seinen Lebzeiten war der Maler weltberühmt.
Even during his lifetime, the painter was world-famous.

lifetime
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during one's lifetime
A fixed expression meaning that something happens while a person is still alive.
Schon zu seinen Lebzeiten war der Maler weltberühmt.
Even during his lifetime, the painter was world-famous.

The word 'Lebzeit' (lifetime) is a compound of the stem of the verb 'leben' (to live) and the noun 'die Zeit' (time). So it literally means 'life-time'.
Die Lebzeit eines Schmetterlings ist oft nur wenige Wochen lang.
The lifetime of a butterfly is often only a few weeks.
This word is used almost exclusively in fixed expressions with prepositions. The most important ones are 'zu Lebzeiten' (during one's lifetime/while one is or was alive) and 'auf Lebzeiten' (for the rest of one's life).
Zu seinen Lebzeiten wurde der Künstler kaum beachtet.
During his lifetime, the artist received little attention.
The expression 'zu Lebzeiten' (during one's lifetime) needs a complement that shows whose life is meant. This is usually done with a possessive pronoun or a genitive.
Zu Lebzeiten meiner Großmutter sah die Stadt ganz anders aus.
During my grandmother's lifetime, the city looked completely different.
Without a preposition, 'die Lebzeit' (lifetime) is often used in the singular in a scientific or statistical context to refer to lifespan. Typical collocations are 'durchschnittliche Lebzeit' (average lifetime) or 'erwartete Lebzeit' (expected lifetime).
Forscher untersuchen die durchschnittliche Lebzeit dieser Tierart.
Researchers are studying the average lifetime of this animal species.
The expression 'auf Lebzeiten' (for life) is often used in a legal or official context. It describes that a right, an office, or an obligation applies until a person's death.
Der Vertrag garantiert ihm eine Rente auf Lebzeiten.
The contract guarantees him a pension for life.
lifetime
'Lebenszeit' and 'Lebzeit' are both connected to the duration of a life. 'Lebenszeit' is by far the more normal word when talking about the whole span of a person's life. 'Lebzeit' is rarer today and appears especially in fixed expressions, for example 'zu Lebzeiten' (during one's lifetime) or 'auf Lebzeiten' (for life). They can be confused because they look almost the same and sound similar. In many everyday sentences, however, 'Lebenszeit' sounds more natural. 'Lebzeit' is used mainly when exactly these fixed expressions fit.

Zu Lebzeiten des Künstlers waren seine Bilder kaum bekannt.
During the artist's lifetime, his paintings were barely known.
Ihre Lebenszeit war kurz, aber sie hat viele Menschen unterstützt.
Her lifetime was short, but she supported many people.