Which Civilization developed & implemented the first solar calendar?

Note : The Egyptians appear to have been the first to develop a solar calendar, using as a fix point the annual sunrise reappearance of the Dog star– Sirius, or Sothis in the eastern sky, which coincided with annual flooding of the River Nile. They constructed a calendar of 365 days, consisting of 12 months of 30 days each,\xa0 with 5 days added at the year’s end. The Egyptians failure to account for the extra fraction of a day, however, caused their calendar to drift gradually into erro.