Corrected entry: The kids and the men are decorating Easter eggs and Ceilie is stuffing a turkey. Shug gets the mail and takes Ceilie upstairs and hands her the letter. When she turns the letter over the date is July 10. But when she reads the letter she says the date is April 18, 1935. So if it's July, how is it Easter?
Corrected entry: When Celie is giving birth to Olivia it says Winter 1909. Later on in the movie when she is in the cloth store and thinks she sees her daughter, Olivia, it says Spring 1909.
Correction: That's wrong. Adam was born first and taken while Celie was sleeping. Olivia is the second born.
It was probably in January (winter) 1909. However, if it was spring, the baby wouldn't be more than 5 months old.
Correction: No, in 1909 she gave birth to her son Adam. Olivia had already been born and given away.
Corrected entry: In town, Celie checks Corrine's baby's diaper to see if she had a diaper on that Celie had stitched with the name Olivia. However, Nettie teaches Celie to read and write after Celie's marriage to Mister.
Correction: Celie can already read, just not very well. When she and Nettie are talking about Mister in the room together and coming up with a plan for when Mister makes a move on Nettie, it is actually Celie who suggests they write. Nettie asks her if she can read good enough and Celie says she can't say that she does. That's when they decide that Nettie will teach her to read better.
Correction: Celie also states she embroidered moons and stars on the diapers. She could have been checking for those, as well.
Other mistake: Mister cooks Shug Avery a breakfast of grits, biscuits and ham, and takes it to her room. She throws the breakfast against the wall. The breakfast leaves a bright yellow and bright red stain on the wall. There was nothing on the tray that could have left those colors on the wall. (00:51:10)
Suggested correction: There absolutely were 2 things on the plate that would have left those colors. When you see the plate up close, you see a red sauce (presumably ketchup or tomato sauce) on the side of the plate, and the yellow comes from the yolks from the sunny-side up eggs he made for her (which he mentions it as he takes the tray into the room). Look more closely at the plate next time. Also, just because the clip mainly shows him TRYING to make grits and biscuits, doesn't mean he didn't make anything else to go with it. The plate he carries up shows several things he made (mostly burnt) but the red sauce was definitely on the plate as well as the eggs. So this is incorrect.
Corrected entry: During the scarification chant, you see Adam being scarred on his right cheek. At the end of the movie when Adam meets Celie for the first time, there is no scar on the right side of his face at all. (00:37:20 - 01:05:20)
Correction: The character that is being scarred in the ritual is not Adam, but Adam's classmate and friend. This friend can be observed as not being Adam in other scenes of the movie.
Correction: That is how long it took for the letter to get from Africa to Celie in rural Georgia.
Yes, it would take months for the letter to arrive which is the point OP is making. It was written in April, received in July, so why is the family painting Easter eggs in July? It's either Easter and the prop department made an incorrect postmark, or it's July and the director choose to have them painting Easter eggs for no apparent reason.