My mother has a multiple entry visa to Canada. She arrived in November to Canada on a visit. So at that time, I believe, her stay was permitted until May (although there is no stamp on the passport about when she can leave). In December, she left Canada to the US and came back on February 18. The passport stamp only indicates when she came in. Does that mean that her stay is automatically extended by 6 months until August 18? Or is it still May?