ÞEGAR

ÞEGAR 'when' is tagged as P (projecting PP) when it introduces an adverbial clause.

(IP-MAT (NP-SBJ (PRO Þetta))
        (BED var)
        (PP (P þegar)
            (CP-ADV (C 0)
                    (IP-SUB (NP-SBJ (NPRS Norðmenn)
                            (VBDI tóku-taka)
		            (NP-OB2 (PRO-PMPD sér-sig))
		            (ADVP-LOC (ADV þar-þar))
		            (NP-OB1 (N-FSAIC bólfestu-bólfesta))))

When ÞEGAR introduces a relative clause it is tagged as WADV (projecting CP-REL). Note that unlike English, ÞEGAR 'when' does not introduce a question (neither direct nor indirect).

(PP (P-D á-á)
    (NP (ADJR-FPDWC fyrri-fyrri)
	(NS-FPDIC öldum-öld)
	(, ,-,)
	(CP-REL (WADVP-2 þegar-þegar)
		(C 0)
		(IP-SUB (ADVP-TMP *T*-2)
			(NP-SBJ (NPRS-MPNIO Norðmenn-norðmaður))
			(VBDI tóku-taka)
			(NP-OB2 (PRO sér-sig))
			(ADVP-LOC (ADV þar-þar))
			(NP-OB1 (N-A bólfestu-bólfesta))))))