Ugh how to edit periods in glow?

Starting to wonder if I should just come here to talk to you ladies as glow tracking is doing my head in... This time my AF was 22/12 to 27/12 and it will only let me have it in the calander till the 26. I try to drag it but won't budge! Plus it says I'm to get AF again starting tm based on my AF that came after my MC and it won't let me delete it. Any ideas? Do you guys track in something different?