[1] sunnudag ‘a Sunday’: That the battle was fought on a Sunday, i.e. that sunnudag modifies the main clause, is the most natural interpretation and is the understanding of Snorri Sturluson (see Context). Alternatively, the word could conceivably be taken with the sem-clause in ll. 3-4, so that the battle is not fought on a Sunday, but is contrasted with pleasant relaxation on a Sunday.