This is arguably the single most common grammar mistake English speakers make in Danish, and it is purely a transfer error. English has one word, "when", that covers a one-off past event ("when I arrived"), a habit ("when it rains"), and the future ("when I get there"). Danish splits "when" into two words and forces you to choose. Get the choice wrong and the sentence isn't just unidiomatic — it's grammatically incorrect to a native ear.
The rule in one line
- da = "when" for one specific, completed event in the past — a single point on the timeline that is over.
- når = "when(ever)" for repeated/habitual events (any tense) and future events.
The trap is that English "when" gives you no signal at all about which one you need. So you have to look past the English and ask: did this happen once, in the past, and is it finished? If yes — da.
Da jeg var barn, boede vi i Aarhus.
When I was a child, we lived in Aarhus. (one finished period — da)
Da hun ringede, sov jeg.
When she called, I was asleep. (single past event — da)
The errors, by sub-type
Sub-type A: a single life period in the past
"When I was young / a child / a student" is one bounded, finished stretch — it takes da. This is where the mistake is most frequent, because the English sounds so habitual.
❌ Når jeg var barn, legede vi altid i skoven.
Incorrect — a single past childhood is one finished period; use 'da'.
✅ Da jeg var barn, legede vi altid i skoven.
When I was a child, we always played in the forest.
Note that altid ("always") inside the clause does not change the choice — the when-clause itself still points to one bounded past period, so da is correct even though the activity within it repeated.
Sub-type B: a single completed action
A one-time action that happened and finished — arriving, meeting, hearing the news — takes da.
❌ Når vi mødtes første gang, regnede det.
Incorrect — a first meeting is a single past event; use 'da'.
✅ Da vi mødtes første gang, regnede det.
When we met for the first time, it was raining.
❌ Han blev meget glad, når han hørte nyheden.
Incorrect — hearing the news once is a single past event; use 'da'.
✅ Han blev meget glad, da han hørte nyheden.
He was very happy when he heard the news.
Sub-type C: confusing a finished past with a habit
The deepest version of the error is treating a finished one-off as if it were a rule of life. Here are two more single-event past clauses that learners wrongly mark with når.
❌ Når jeg flyttede til Danmark, kunne jeg ikke tale dansk.
Incorrect — moving to Denmark happened once; use 'da'.
✅ Da jeg flyttede til Danmark, kunne jeg ikke tale dansk.
When I moved to Denmark, I couldn't speak Danish.
❌ Hun smilede, når hun så billedet i går.
Incorrect — 'yesterday' pins it to one past moment; use 'da'.
✅ Hun smilede, da hun så billedet i går.
She smiled when she saw the photo yesterday.
The wrinkle: past når IS correct for a repeated past
Here is the part that makes the rule feel slippery — and why "når is never for the past" is a dangerous oversimplification. When a past event repeated — "whenever, back then" — når is exactly right. The deciding factor is frequency, not tense: one finished event → da; a recurring event → når, even in the past.
Når jeg var syg som barn, lavede mor altid suppe.
Whenever I was ill as a child, Mum always made soup. (repeated past — når is correct)
Når vi var på ferie, stod vi tidligt op.
When(ever) we were on holiday, we got up early. (recurring past — når)
Compare the minimal pair, which captures the whole rule in two sentences:
Da jeg så ham, blev jeg glad.
When I saw him (that one time), I was happy. (single past — da)
Når jeg så ham, blev jeg glad.
Whenever I saw him (back then), I was happy. (repeated past — når)
Root cause and the fix
The root cause is a one-to-two mapping: English "when" → Danish da or når. English simply doesn't encode the once-versus-repeated distinction in the word, so there's nothing in the source language to transfer. You have to add the information that English leaves out.
The corrective rule, memorised as a rhyme: "Da, dengang — når, hver gang." — da for that one time back then; når for every time (and the future). Before you write når about the past, ask: "Could I say 'whenever' here?" If no, it must be da.
Common Mistakes (summary table)
| Situation | Wrong | Right |
|---|---|---|
| Single past period | ?Når jeg var ung… | Da jeg var ung… |
| Single past action | ?Når toget ankom… | Da toget ankom… |
| Repeated past | — | Når jeg var syg, … (correct!) |
| Future event | ?Da jeg kommer hjem… | Når jeg kommer hjem… |
For the full reasoning and more contrasts, see Da vs. når. For these conjunctions in their wider context (plus mens, før, efter at), see Subordinating conjunctions of time.
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Start learning Danish→Related Topics
- Da vs Når: Choosing 'When'A2 — How to choose between da and når for 'when' — da for a single past event, når for habitual or future ones.
- Subordinating Conjunctions of Time: Da, Når, MensA2 — How to say 'when', 'while', 'before', 'after' and 'until' in Danish — including the crucial da vs når split for past versus repeated events.
- Conjunctions of Cause and Reason: Fordi, Da, EftersomA2 — How to give reasons in Danish — fordi for the default 'because', da and eftersom for a known reason, and how they differ from the coordinating for.
- Inversion After a Fronted ElementA1 — Whenever a non-subject opens a Danish main clause — an adverb, object, prepositional phrase, or subordinate clause — the verb stays second and the subject moves behind it.