Continuity mistake: When Sophie is in her bedroom with Ali and Lisa after they have just arrived, Ali has a scarf and she places it on her shoulders. In the very next shot it it now suddenly wrapped around her shoulder, even though she didn't have time to wrap it around. (00:07:40)
Continuity mistake: When Sam and Harry get out of their separate taxis near the start, there is a huge amount of rope on the harbour. Camera cuts and it's now disappeared and is not trailing from the boat. (00:07:50)
Other mistake: When Harry Bright and Sam Carmichael are standing on the dock in Greece after missing the boat, Harry pulls out his invitation and references the wedding in the invitation, but the envelope is sealed. (00:08:20)
Continuity mistake: When Tanya and Rosie sit down on the boat on the way to the island, as they sit down Tanya has her hands in her lap. In the next shot they're up by her neck. (00:08:50)
Continuity mistake: When Sky is getting his hat and cigar as "props" for his stag party, as he leaves the room wearing the hat and holding the cigar. In the second shot as he walks past Sophie, there is a long loose cord hanging down from the brim of the hat - which wasn't there in the first shot. (00:10:00)
Continuity mistake: When Tanya and Rosie arrive at the island, they get off the boat and walk up the pier. They break into song with Donna (who is walking towards them) but as the shot keeps changing, the two old men standing on the pier disappear and re-appear every time the camera changes. (00:11:25)
Continuity mistake: When Sky hands Tanya and Rosie a drink when they first arrive on the island and meet him on the courtyard, Tanya raises her glass and begins to drink. Then when the shot changes her hand is back down by her waist. (00:15:25)
Continuity mistake: When Donna breaks the shutter, her reaction is different from the angle looking into the room than it is from the inside shot. (00:16:20)
Continuity mistake: During "Money, Money, Money" Donna walks into the kitchen and all the staff are sitting at the table. They hurriedly get up and start working, and a newspaper is left right beside the large fish on the table. When the shot goes back with the table visible, the newspaper has gone. (00:17:35)
Continuity mistake: When Donna, Tanya and Rosie are on the couch talking, Tanya asks Donna "if she's getting any." As she asks her this, the shot switches angles. And as it does, the towel that Tanya is wearing on her head changes from dangling behind her shoulder to suddenly hanging in front of it. (00:21:50)
Continuity mistake: When Sophie is hurrying all three potential fathers into the goathouse, Sam is the last one in. As he walks in we see his bag strap slide down from his shoulder to his elbow. As the shot changes, the strap is now instantly back up on his shoulder. (00:22:25)
Continuity mistake: When Donna climbs on top of the goathouse after seeing Sam, Bill and Harry, and begins to sing "Mamma Mia", as she rolls around all over the roof her dunagrees (especially the knees) become dirty. However the amount, prominence and position of the dust and dirt on her clothing changes a few times during the whole scene. (00:26:10)
Continuity mistake: Soon after arriving, Tanya and Rosie are at a bar and suddenly Donna comes out in tears. Tanya is just receiving a cocktail from Pepper, the bartender. Rosie and Tanya then hurry after Donna - and during the rest of this scene, the amount of drink in Tanya's cocktail keeps lowering then rising. (00:29:45)
Continuity mistake: By the end of the song "Chiquitita", Donna has a red rose in the side of her head (positioned in her hair) after Rosie put it in there. As the shots differ, in some shots the red rose, which should be visible (judged by the amount of the side of Donna's head we can see), is not there. It appears and then disappears a few times and is not due to the angle. (00:32:10)
Continuity mistake: When Meryl Streep closes the bedroom door in the scene right before "Dancing Queen", you see Julie Walters' reflection in the mirror next to her, hands on her hips. In the next shot Streep turns to face Walthers, who now suddenly hasn't got her hands on her hips anymore. (00:34:15)
Continuity mistake: When Tanya and Rosie are talking to Donna in the bedroom just before the "Dancing Queen" number, they are talking about how bad Donna used to be. Rosie then puts a hat on Donna and Tanya puts a green feather boa on Donna's shoulders - twice - between shots. (00:34:50)
Visible crew/equipment: When singing Dancing Queen an extra is seen falling off a ladder. If you look at the front of his shirt, a safety cable can be seen. (00:37:15)
Continuity mistake: On the boat when they are singing Our Last Summer, Sophie is seen sitting next to Bill. In this shot she is holding a picture of Bill in her hands. The camera cuts and now Bill is holding the photo. (00:40:45)
Revealing mistake: During the "Lay Your Love" song, when Sophie and her boyfriend are in one of the corners of the beach, sneaker footprints are seen. Given that the tide is constantly wiping off their bare footprints, the tracks most surely belong to a crew member. (00:44:20)
Continuity mistake: During the song "Lay All Your Love on Me" on the beach, when Sophie lies back and then Sky is on top of her, in this closeup we see Sophie's wearing something else over her swimsuit. It's visible below her waist and as she lifts her right leg. (00:45:00)
Answer: Sophie finds Donna's diary from 1979, being the year Sophie was conceived meaning she was born in 1980 (as the diary entries are from July/August). So the movie is set in 2000.