Days, Months, and Seasons | Icelandic Grammar

The calendar words are among the first nouns you will need, and Icelandic handles them with a few small surprises for English speakers. Two stand out: days and months are written in lowercase (unlike English), and saying 'on Monday' changes the noun's case depending on whether you mean one specific day or every Monday. This page gives you the vocabulary — the seven days, the twelve months, the four seasons — and the grammar of when an event happens. Full date formatting (the 5th of June, etc.) lives on Dates and Time; the spelling rule itself is on Capitalisation.

The seven days — all masculine -dagur compounds

Every weekday name ends in -dagur ('day'), and because dagur is masculine (kk), all seven days are masculine (kk). That is a gift: you never have to wonder about their gender. They are compounds — fimmtudagur is literally 'fifth-day' — and like all compounds they take stress on the first element.

Icelandic	English	Literal sense
mánudagur (kk)	Monday	moon-day
þriðjudagur (kk)	Tuesday	third-day
miðvikudagur (kk)	Wednesday	mid-week-day
fimmtudagur (kk)	Thursday	fifth-day
föstudagur (kk)	Friday	fast-day
laugardagur (kk)	Saturday	bath/washing-day
sunnudagur (kk)	Sunday	sun-day

Notice the numbering logic: the week is counted from Sunday, so þriðjudagur ('third-day') is Tuesday and fimmtudagur ('fifth-day') is Thursday. Miðvikudagur is the 'mid-week day'. And famously, laugardagur is 'washing day' — Saturday was the traditional day for the weekly bath.

Í dag er miðvikudagur.

Today is Wednesday. — the day name as a plain predicate noun, nominative, lowercase.

Laugardagur er besti dagurinn.

Saturday is the best day. — subject, nominative, masculine.

💡

All seven days are masculine because they all end in the masculine noun dagur. One gender to remember for the whole set.

Lowercase, not capitalised

In English, Monday and June are always capitalised. In Icelandic they are not — days, months and seasons are ordinary common nouns and stay lowercase unless they happen to start a sentence. This is one of the most persistent transfer errors, because the English habit is so deeply ingrained.

Ég kem á mánudaginn.

I'm coming on Monday. — mánudaginn is lowercase mid-sentence.

Afmælið mitt er í júlí.

My birthday is in July. — júlí lowercase.

'On Monday' — the case logic

Here is the grammatical heart of the page. To say an event happens on a day, Icelandic uses the preposition á, but the case it assigns — and whether you use the article — depends on your meaning.

A specific, single day: á + accusative with the article

For one specific day — typically this coming Monday or last Monday, a single definite occurrence — you use á plus the accusative singular with the definite article: á mánudaginn. The -inn ending is the suffixed article in the accusative; it is what makes the day that day, the definite one on the calendar.

Day	'on (this/that) _'
mánudagur	á mánudaginn
þriðjudagur	á þriðjudaginn
miðvikudagur	á miðvikudaginn
fimmtudagur	á fimmtudaginn
föstudagur	á föstudaginn
laugardagur	á laugardaginn
sunnudagur	á sunnudaginn

Við hittumst á föstudaginn.

We're meeting on Friday. — one specific upcoming Friday → á + accusative + article (föstudaginn).

Ég fór til tannlæknis á mánudaginn.

I went to the dentist on Monday. — one specific past Monday, still á mánudaginn.

💡

The distinguishing point most courses skip: á mánudaginn (accusative with the article) means a definite single Monday — 'this Monday' or 'that Monday'. The article -inn is doing the work of 'the (one we mean)'. English's bare 'on Monday' hides this definiteness, so learners under-use it.

Every such day (habitual): á + dative plural

For a habitual, recurring event — 'on Mondays', every Monday — you switch to the dative plural: á mánudögum. The plural says 'Mondays' generally, and the dative is what á takes in this recurring sense. Watch the spelling: the -dagur ending becomes -dögum in the dative plural, with the u-umlaut turning the a of dag- into ö.

Day	'on ___s (every)'
mánudagur	á mánudögum
þriðjudagur	á þriðjudögum
laugardagur	á laugardögum
sunnudagur	á sunnudögum

Ég fer í sund á mánudögum.

I go swimming on Mondays. — habitual, every Monday → á + dative plural (mánudögum).

Búðin er lokuð á sunnudögum.

The shop is closed on Sundays. — recurring rule → dative plural sunnudögum.

Hún vinnur ekki á laugardögum.

She doesn't work on Saturdays. — habitual → laugardögum, with the u-umlaut a → ö.

So the contrast to lock in is á mánudaginn (this/that one Monday) versus á mánudögum (Mondays in general). Choosing between them is choosing between a single appointment and a standing habit.

The twelve months — loanwords, take í

The month names are borrowed from Latin and look familiar. They are nouns, written lowercase, and to say something happens in a month you use the preposition í plus the month (which stays in the same form — these don't decline in everyday use): í janúar, í júní.

Icelandic	English	Icelandic	English
janúar	January	júlí	July
febrúar	February	ágúst	August
mars	March	september	September
apríl	April	október	October
maí	May	nóvember	November
júní	June	desember	December

Skólinn byrjar í ágúst.

School starts in August. — í + month, lowercase ágúst (note the accents á and ú).

Það snjóar oft í desember.

It often snows in December. — í desember; desember with one s.

Við förum til Spánar í júní.

We're going to Spain in June. — í júní (note the accents on both vowels).

Mind the accents: janúar, febrúar, maí, júní, júlí, ágúst, október, nóvember, desember all carry diacritics. Maí and júní are easy to confuse in spelling — maí (May) has the í at the end; júní (June) has one on each vowel.

The four seasons

The seasons are everyday nouns of mixed gender — worth tagging carefully:

Icelandic	Gender	English
vor	hk (neuter)	spring
sumar	hk (neuter)	summer
haust	hk (neuter)	autumn / fall
vetur	kk (masculine)	winter

Three of the four — vor, sumar, haust — are neuter (hk); only vetur is masculine (kk). There are two everyday season constructions worth knowing: í sumar means 'this (coming) summer' — a single, current season — while á sumrin means 'in the summers', the recurring sense (dative plural with the article). The same pattern gives í vetur ('this winter') versus á veturna ('in the winters'). This is the same single-occurrence-versus-habitual split you saw with the weekdays:

Á Íslandi er bjart á sumrin.

In Iceland it's bright in the summers. — sumar is neuter; á sumrin for the recurring season.

Það er kalt á veturna.

It's cold in the winters. — vetur is masculine; á veturna for the habitual.

Common Mistakes

❌ Ég kem á Mánudaginn.

Incorrect — days are lowercase in Icelandic; capitalising is English transfer.

✅ Ég kem á mánudaginn.

I'm coming on Monday.

❌ Afmælið mitt er í Júlí.

Incorrect — months are lowercase: júlí.

✅ Afmælið mitt er í júlí.

My birthday is in July.

❌ Ég fer í sund á mánudaginn (meaning 'every Monday')

Incorrect — for a habitual, recurring event use the dative plural á mánudögum; á mánudaginn means one specific Monday.

✅ Ég fer í sund á mánudögum.

I go swimming on Mondays.

❌ Búðin er lokuð á sunnudagum.

Incorrect — the dative plural takes the u-umlaut: a → ö, so sunnudögum, not sunnudagum.

✅ Búðin er lokuð á sunnudögum.

The shop is closed on Sundays.

❌ Skólinn byrjar á ágúst.

Incorrect — months take í ('in'), not á: í ágúst.

✅ Skólinn byrjar í ágúst.

School starts in August.

Key Takeaways

All seven days are masculine (kk) because they end in dagur — one gender for the whole set.
Days, months and seasons are lowercase — resist the English instinct to capitalise.
'On (this) Monday' = á + accusative with the article: á mánudaginn, a definite single day.
'On Mondays' (habitual) = á + dative plural: á mánudögum, with the u-umlaut a → ö.
'In a month' uses í: í janúar, í júní. Mind the accents (júní, ágúst, október, desember).
Seasons: vor, sumar, haust are neuter (hk); vetur is masculine (kk).

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