Rotate sets of images in HTML pages according to the month

Below is described shortly what I need to do. HTML page1 has 10 images in several places. I want to display : a1-1, a1-2,..., a1-10 images all days from january to june (all years) on this page b1-1, b1-2,..., b1-10 images all days from july to december (...) HTML page2 has 7 images in several places. I want to display : a2-1, a2-2,..., a2-7 all days from january to june (all years) b2-1, b2-2,..., b2-7 all days from july to december (all years) Same for other HTML pages, all with different sets of images. Important : Some pages will have 10 images, others 7, others 20, etc. I'll have at least 100 different pages. The pages and images are all different. The goal is to make the pages look different in time. (They are travel articles.) The pages will be static. PHP is available. No database, unless you think it's absolutely needed. Do you think the script will affect the speed of the pages ? You won't need to make the pages, I'll do them myself using a ready-made template. Your work is just the script that make the images change in time. Thank you for your attention.