noun
calendar
A2
Kalender: means 'calendar' (monthly or yearly schedule). It is a masculine noun (der Kalender). Plural is Kalender (unchanged). Genitive singular adds -s (des Kalenders). Regular declension otherwise; no umlaut. Useful for dates and appointments; not a verb and has no prepositions or auxiliaries.
Examples
Ich markiere den Geburtstag im Kalender.
I mark the birthday on the calendar.
Die Sekretärin trug die Termine in den Kalender ein, als der Chef sie bestätigte.
The secretary entered the appointments into the calendar when the boss confirmed them.
Ich habe einen Kalender.
I have a calendar.
Details
Mnemonics
Looks like English 'calendar' — same meaning.
der — imagine a male office worker writing dates on the calendar.
Notes
Used both for wall calendars and schedules. Plural usually identical in form.