Dates have been calculated by references in the episodes and by the weather in each episode. The order episodes appeared is assumed to be the order of events, with the exception of Evil Eye where the promotion of Tony Rizzo to detective showed that this episode was clearly out of order.
Many fans assume that the events of the pilot episode, The Illusion, took place within the same year as the subsequent episodes in the first season, but there is no evidence to support this. In fact, based on several things, it is possible that The Illusion took place a year earlier, in 1995. First of all, there is the fact that The Illusion was filmed in the summer of 1995, which would have been as much as a year earlier than the next episode, Zero Hour, was filmed. Looking at things in The Illusion itself, we can also see differences between it and later episodes that would imply that the events of The Illusion happened at least several months earlier. Leo's hair was brown, while in Zero Hour, the next episode, and in all episodes afterwards, it was graying. There was a noticeable difference in Rollie and Angie's relationship and in Angie's personality in The Illusion, which would make sense if Angie had just recently finished college and went to work for Rollie. There was also a big difference in the relationship between Leo and Francis. It was very clear by Leo's attitude that he and Frank had not been partners for long (he was partnered with Leo 3 months previously). That "new partnership" feeling was not present in subsequent episodes.
1949 - Leo McCarthy is born (date was on Leo's gravestone in Unfinshed Business)
Between March 1964 and spring of 1967 or 1968 - Rollie Tyler is born (based on Rollie revealing in Vigilantes that he was younger than a character who was born on Feb. 19, 1964 and the fact that Rollie had been in the F/X business for at least ten years as of The Illusion, which, as stated above, took place either in 1995 or 1996) (Note: I am attempting to narrow this date further)
1972 or 1973 - Angie Ramirez is born (based on age being mentioned as 24 in Siege)
Late 1977 or 1978 - Rollie comes to the U.S. (this is assuming that Rollie came with his father).
1991 (possibly late spring or summer) - Manny Ramirez is accidentally killed in an explosion on a movie set.
1994 (?) - Rollie meets Taya Kwan in Hong Kong and has an affair with her.
Pre- 1995 or 1996 - Dan Waters works with Leo on a case where they find a body in a freezer. Dan made the comment "He sleeps amongst the fish sticks".
Pre-1995 or 1996 - Dan Waters saves Leo's life when he pulls him from an apartment doorway just before a shotgun blast comes through the door.
Early 1995 or 1996 - Francis Gatti is promoted to the rank of Detective.
Late Spring/Summer 1995 or 1996 - Rollie is set up for murder by jewel thieves. He then foils their plans with the help of (new friend) Lucinda, as well as Angie, Francis and Leo.
Late Spring/Early Summer 1996 - Wayne Harmon and the 7th Brigade militia group try to bomb the Hayes building in New York. The bombing is foiled through an elaborate plan that has Wayne believe his bomb has already been detonated.
Late Spring/Early Summer 1996 - Angie is framed for the murder of Nick Breen, the director she blamed for her father's death.
Summer 1996 - Rick Forsythe is killed during a stunt when a burning car crashes into the car he is on.
Summer/Fall 1996 - Dan Waters is killed in a hit and run accident during a drug bust. Midtown South (NYPD) helps the feds bring down a counterfeiting ring.
Late Fall/Winter - Victor Loubar poses as Rollie as part of a plot to steal the plans to a top-secret weapon called a smart grenade. In the end, Loubar is shot by Elena Serrano and falls into a river.
Spring/Summer 1997 - Leo McCarthy is killed by a bomb in a warehouse. Rollie and Angie meet Palmira Sanchez.
Summer 1997 - Victor Loubar attempts to sell a bio-weapon to Willem Brink, but is foiled by Rollie, Angie and Elena Serrano.
Summer 1997 - The "Dreaming" Rollie had as a child comes true when Luther Cale, the man who tried to kill him when he was a child, steals two Aboriginal artifacts called the Soul Stones and brings them to New York to sell. Rollie and Cale battle in the end, and Cale is killed.
November 1997 - Rollie, Angie and Mira capture the jewel thief Sebastian. (Date obtained from computer screen image.)
December 4th or 5th, 1997 - Victor Loubar kidnaps Rollie Tyler, drugging him and leaving him in a basement in New York's Chinatown.
December 7th, 1997 - Red Storm wrap party. Victor Loubar seduces Angie Ramirez while wearing the face of Rollie Tyler.
December 8th, 1997 - Angie Ramirez discovers that the man she slept with the previous night was not Rollie Tyler. Loubar releases Rollie. Loubar tries to assasinate the visiting Chinese Trade Minister and is foiled by Angie and Rollie. Angie shoots Rollie in the arm, and Loubar disappears again. (Date obtained from computer screen showing list of events at the Galen Conference Centre.)