My period came in 2 weeks early last month and this month its a day late, what could be the causes?

Some possibilities: Many women have occasional variation of their menstrual period timing, some spotting between periods, a heavier or lighter period, a longer or shorter period, or even a missed period. Having one of these symptoms doesn’t necessarily mean a medical problem, but a visit to one’s primary care or Ob-Gyn doctor is a good idea if symptoms are persistent, recurring, or worrisome.