Board Thread:Character Discussion/@comment-15736398-20140815200340/@comment-15736398-20140816034848

Emma's birthday is the exact same day that the Curse was first cast (we're shown this in the Pilot, and it's repeatedly stated throughout Seasons 1 and 2 that it's been 28 years since that one single event changed everyone's lives). The year that Emma and Neal first met (2001) was also derived from that one central fact (the Curse having been cast 28 years previously on Emma's birthday), as was Henry's age at the beginning of the series.

Emma being 18 at the time she conceived Henry is also a fact that's been repeated numerous times throughout the series to date, and is supported and reinforced by Henry's stated age at the beginning of the series. His stated year of birth (2001) also supports and reinforces the idea that Emma being 18 when she gave birth to him is a factual 'pillar' upon which much of the series' overall narrative framework has been built to date.