Your client seems unsure about the order of things like days or month. When you say something happens on Thursday, they may not immediately understand that the thing that happens on Monday is before.
They will take longer to process instructions that include a lot of figuring out of things in order. They will also find it hard to give lists of things or order items alphabetically.
Use graphical aids to help people understand sequences.
For example, draw diagrams, flowcharts or time lines.