Canute sent Aelfgifu with their eldest son Svein to rule Norway, in 1030. Their rule was so harsh though that the Norwegians rebelled against them, and they were driven out, in 1035, while Svein died of wounds in Denmark shortly after, probably in 1036. In Norway this period is known as Aelfgifu's Time, remembered for heavy taxes.
Aelfgifu was determined that her second son should be the next English king, on the death of Canute the same year, in 1035. She bribed the noblemen, supposedly, to accept Harold as a temporary king, or regent, while Harthacnut, Queen Emma's son by the late King of England, was away in Denmark, at war with the Norwegian king Magnus I, and the Swedes under their king Anund Jacob.
Apparently, Aelfgifu was part of a plot to murder Alfred Atheling, son of Queen Emma by Ethelred, who was on his way to see his mother after a long exile in Normandy. None could oppose Harold and the English supporters of his claim, especially after his Huscarls laid claim on the treasury, and he was crowned King of England in 1037. Aelfgifu fell into obscurity after Harold's death from a stroke, as believed in 1040, and the crowning of Harthacnut, the legitimate heir to Cnut and also the King of Denmark.
Her age, along with her son's, is entirely based on the evidence which is available on the date of King Canute's birth, as it is the supposition the couple were the same age, while no definite information survives on the date for marrying of the two. It is maybe the case they were married in 1016, the year before Canute was to marry his court queen Emma, although it is perhaps even more likely it was in 1004, when Canute may have been with his father Swegen Forkbeard's raiders, and the infamous Thorkel the High, as they made an attempt on the wealthy city of Norwich. It was a period of extensive Viking attacks throughout England, and the presence of Canute near the Danelaw, in Northhampton, or even in York, the Earldom of her father, Aelfhelm, is entirely plausible. So she was at the latest, born in the mid 990s, although an earlier birth in the mid-980s is likely.
Gytha was the daughter of Thorgils Spregaleag (last king of Scania (Ohlmarks) & Sigrid. Thorgils was the son of Styrbjorn The Strong (son of Olaf, King of Sweden) & Thyra Haraldsdottir (the daughter of Harald Bluetooth).