jederzeit
anytime
At any time; always.
Sie können mich bei Fragen jederzeit anrufen.
You can call me anytime if you have questions.

anytime
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anytime
At any time; always.
Sie können mich bei Fragen jederzeit anrufen.
You can call me anytime if you have questions.

The word is a compound of 'jeder' (each/every) and 'Zeit' (time). So it literally means 'at any time' and is easy to remember.
Das Museum ist jederzeit für Besucher geöffnet.
The museum is open to visitors anytime.
As an adverb, 'jederzeit' (anytime) can stand flexibly in the sentence. It can stand in position 1, which creates emphasis, or inside the sentence after the conjugated verb.
Jederzeit können Sie eine Pause machen.
You may take a break anytime.
'Jederzeit' (anytime) often sounds somewhat more formal and binding. It is frequently found in service and business language to express constant availability or possibility.
Der Vertrag ist jederzeit kündbar.
The contract can be canceled at any time.
always
'immer' and 'jederzeit' both have to do with time without a fixed limit. 'immer' means that something happens constantly or on every occasion. 'jederzeit' means more like: at any time, whenever one wants or whenever it is necessary. That is why you say 'Du kannst jederzeit anrufen' (You can call anytime) when the time is open. 'Du rufst immer an' (You always call), on the other hand, means that it happens regularly or constantly. The words can be confused because both come close to 'at all times', but 'jederzeit' emphasizes possibility, while 'immer' emphasizes repetition or duration.

Wenn du Hilfe brauchst, kannst du mich jederzeit anrufen.
If you need help, you can call me anytime.
Bei wichtigen Fragen fragt sie immer zuerst ihren Kollegen.
When she has important questions, she always asks her colleague first.