Looks like a ‘regional’ difference. Like if one of the Simulators is (for whatever reason) set to UK (thus, ‘5 February’) and one is set to US (thus ‘February 5’).
Best suggestion would be to use capabilities ‘locale’ and ‘language’ when starting Appium Client for your simulators. Whole discussion here:
NOTE: this only works on Simulators. Real device you have to configure manually.