Emma arrives in Storybrooke on October 22. "True North" takes place a month later in late November. Approximately two weeks later (three weeks after Emma becomes sheriff) Henry looses his book ("The Fruit of the Poisonous Tree") There is a time gap of about two months be fore the next episode "Skin Deep", which takes place on Valentines Day. On February 19, Kathryn goes missing. Gold makes a deal with Regina some time between these two events (February 14-19). One week later, in "Stable Boy", Emma finds Kathryn (Feb. 21-26). Marry Margret is released from prison and goes back to teaching within the next few days (late Feb.- early March). That night, Emma runs away with Henry. The next day, Regina gives Emma a poisoned apple turnover that Henry eats. Within hours Emma fights a dragon, saves Henry, breaks the curse, and is sent to the Enchanted Forest. One week later (Lady of the Lake), Henry tries to rescue his mom and grandma (Early March). Less than a month after the curse is broken Ruby goes through her first wolf phase (Child of the Moon). In this episode it is mentioned that Mary Margaret was suspected of murder a few months ago. That is an error. It was a month and a half at most. Within the next two days, Emma and Mary Margaret return to Storybrooke (March-Early April 2012). The next day, Cora frames Regina of murdering Archie. A few days (maybe weeks) later, Archie returns. Later that night, Gold tries to pass the town line, Belle gets shot, and Hook gets hit by a car. The next day, Gold asks Emma to help him find his son. An unspecified amount of time later (no more than a few days) they leave for New York (March to early May). The next day (approximately) Henry meets his father Neal/Baelfire. Two days later, Regina plots to kill Mary Margaret (Welcome to Storybrooke). The next day (approximately) Marry Margaret confronts Regina who shows her her heart. One week later, Marry Margaret tells David (Selfless, Brave, and True). It is unclear how much time passes before the next episode "Lacey" (possibly a time gap of a few weeks). In this episode Greg and Tamarra kidnap Hook, who they release the next day in "The Evil Queen". It is unclear how much time passes within this episode (a few days at most). Regina is kidnapped and tortured by Greg and Tamara. That same day, Neal is sent through a portal. The next day Greg and Tamara atttempt to destroy Storybrooke. They don't succeed but manage to kidnap Henry and take him to Neverland. His family leaves to find him (March-June 2012). Five days later, Ariel arrives in Storybrooke. No more than a few days later, Henry's famiily returns to Storybrooke. About two days later, everyone but Emma and Henry are sent back to the Enchanted Forest (Late March to Late June). There is a time gap here of one year before Emma and Henry return to Storybrooke (Late March- Late June 2013). It is only a matter of days (weeks at most) before the curse is broken and Mary Margaret has a baby. The next day, Emma and Hook are sent back in time. They manage to make it back but accidently take Maid Marian and Elsa with them (April - July 2013). The first half of season 4 takes place over an unspecified amount of time but ends around November 6, 2013 when the fairies are reported missing. There is a time gap of six weeks before the fairies are released (December 18 approximately). Three weeks later, Regina learns about Zelena (January 8, 2014 approximately). Regina wastes almost no time before planning to go to NY and warn Robin. Her plans are delayed slightly by Cruella. A few days later, Emma and Regina find Lily and Robin Hood. Shortly after, they return to Storybrooke, leading to the events of "Operation Mongoose" (Mid January 2014)
Season 1: 4-5 months
Season 2: 1-3.5 months
Season 3a: 1-2 weeks
Gap: 1 year
Season 3b: No more than a few weeks
Season 4a: 4 months?
Gap: 6 weeks
Season 4b: 3-4 weeks