Learn Hardcore German: An Feiertagen bleibt Marias Büro grundsätzlich geschlossen. - On public holidays Maria’s office is basically closed.

an Feiertagen (no article, dative plural) = “on holidays in general.” It expresses a general rule.
am Feiertag = an dem Feiertag (singular, specific) = “on the holiday.” This points to one particular holiday.
an den Feiertagen (with article, dative plural) = “on the holidays,” referring to a specific, known set (e.g., the coming public holidays).

What case is Feiertagen, and why does it end in -n?

It’s dative plural. Most German nouns add -n in the dative plural (unless the plural already ends in -n or -s).
Singular: der Feiertag → Plural: die Feiertage → Dative plural: (an) den Feiertagen / (an) Feiertagen.

Why use bleibt … geschlossen instead of ist … geschlossen?

Both are correct, but there’s a nuance:

bleibt geschlossen highlights the state of remaining closed (it stays closed throughout those times). It’s natural for rules/opening hours.
ist geschlossen simply states the state at that time.
On signs you’ll also see hat geschlossen (“is closed”). For habitual rules, bleibt is especially idiomatic.

What does grundsätzlich mean here?

Here grundsätzlich means “as a rule,” “generally,” or “by default.” It doesn’t mean “fundamentally” in a philosophical sense. Synonyms in this context: in der Regel, normalerweise.

Is Marias Büro correct without an apostrophe? Should it be Maria’s Büro?

Yes, Marias Büro is correct German. No apostrophe is used for the genitive of most names.
Use an apostrophe only when the name already ends in an s-like sound (s, ß, x, z): e.g., Jens’ Auto.
You can also say das Büro von Maria, which is perfectly idiomatic, especially in spoken German.

What’s the subject and basic structure of the sentence?

Subject: Marias Büro
Finite verb (2nd position): bleibt
Predicative adjective: geschlossen
Adverb: grundsätzlich
Adverbial prepositional phrase of time: An Feiertagen
Overall: Time phrase first → verb in 2nd position (V2 rule) → subject → middle-field elements → predicate complement.

Why does the sentence start with An Feiertagen?

German allows fronting an element (here, the time phrase) for emphasis or flow. In main clauses, the finite verb must still be in 2nd position, so bleibt comes next. You could also say:

Marias Büro bleibt an Feiertagen grundsätzlich geschlossen. (neutral)
Grundsätzlich bleibt Marias Büro an Feiertagen geschlossen. (emphasizes the general rule)

Where should grundsätzlich go, and can I move it?

Yes, it’s movable within the “middle field.” Common and natural options:

Marias Büro bleibt an Feiertagen grundsätzlich geschlossen.
An Feiertagen bleibt Marias Büro grundsätzlich geschlossen.
Grundsätzlich bleibt Marias Büro an Feiertagen geschlossen.
The placement fine-tunes emphasis (rule vs. time vs. subject) but all are grammatical.

Is geschlossen an adjective or a participle here?

It’s the past participle of schließen, used predicatively like an adjective to denote a state: bleibt geschlossen = “remains closed.” The opposite is geöffnet (“open”).

Could I use zu instead of geschlossen?

Colloquially, yes: Das Büro ist zu. But for formal or neutral style (rules, notices), geschlossen is preferred. zu is casual.

Why is schließen spelled with ß but geschlossen with ss?

Spelling follows vowel length: schließen has a long vowel (ie), so ß is used; geschlossen has a short vowel before the s-sound, so it takes ss. This is normal in German derivation.

Why are Feiertagen and Büro capitalized, but grundsätzlich and geschlossen are not?

German capitalizes nouns: der Feiertag, das Büro. Adverbs and adjectives like grundsätzlich and geschlossen are lowercase unless they begin a sentence or are part of a title.

Can I say zu Feiertagen or bei Feiertagen?

The idiomatic choice for “on holidays” is an Feiertagen.

zu is used with some festive periods: zu Weihnachten, zu Ostern.
bei works with conditions (e.g., bei schlechtem Wetter) or events, but bei Feiertagen for “on holidays” sounds unnatural.

How do I talk about specific festivals like Christmas or Easter?

For major festivals you commonly use either an or zu:

an Weihnachten / zu Weihnachten
an Ostern / zu Ostern
Both are widely accepted; zu can sound slightly more idiomatic with festivals, while an is standard with days/dates.

What’s the difference between Feiertage, Ferien, and Urlaub?

Feiertage = public/bank holidays (official days off).
Ferien = school or general holiday periods (e.g., summer vacation).
Urlaub = time off work (vacation leave).

How would I express this in other tenses?

Past (habitual in the past): An Feiertagen blieb Marias Büro grundsätzlich geschlossen.
Future (still a rule): An Feiertagen wird Marias Büro grundsätzlich geschlossen bleiben.
Present perfect for a specific past occurrence (not habitual): An Feiertagen ist Marias Büro geschlossen gewesen.

Is am Feiertag always singular?

Yes, am = an dem, so it’s singular: am Feiertag = “on the holiday.” If you want plural with an article, use an den Feiertagen. For a general statement without an article, an Feiertagen is best.

Could I replace grundsätzlich with something else?

Yes. Natural alternatives include:

in der Regel
normalerweise
im Allgemeinen
Example: An Feiertagen bleibt Marias Büro in der Regel geschlossen.