"Frimærket blev købt af en journalist mens hun var udenlands."
Translation:The stamp was bought by a journalist while she was abroad.
'While' and 'when' are interchangeable in English in this context and both should be accepted.
Is this type of sentence more common in Danish than "En journalist kobte en frimaerket mens hun var udenlands"? When do you use the first and when the second one? Or it doesn't matter?