Since this is tagged as web-design:
Although your purpose for these calendar images is not clear, in order to create this in the most dynamic way, I'd recommend using HTML's little know
<time> element (which is supported back to IE9) and CSS as opposed to creating a bunch of variation images because it's much easier to update.
Here's a basic structure you could use (pulled from Craig Buckler's article on the subject), you could just replace the text with what you need.
<time datetime="2014-09-20" class="icon">
With some added styling, you can create something quite similar to what you're wanting. You could even create the rings on top by using pseudo elements.
If you use a preprocessor like SCSS, you could make changing the color scheme (even with gradients) could be as simple as changing one variable.