Glow period accuracy ???

Chanel
Ladies how accurate has Glow been on the start of your period? Glow says I'm suppose to start today but it's a no show and I'm pretty spot on month to month never really late! My BBT are still high also. 
I have other charting apps and they all give me different days I don't know which to believe. Fertility friend says tomorrow ... 
How has your experience been with Glow and accuracy? I'm too scared to take a test for it may be to early!