Device/Smartphone: iPhone (any version)
On most mobile smartphones and iPhones when you’re synchronizing your calendar or emails – for all intents and purposes we will call this the ‘cloud’ – the devices are smart and only synchronize the last few weeks or month. Doing this avoids downloading the last 10 years of emails and calendar events to your phone, taking up space that could otherwise be used for selfies.
Sometimes this is a problem and you need to go back a bit further then the default history date.
To change sync history, in your phone’s Settings -> Mail, Contacts, Calendars -> scroll down to Calendars section where you will see Sync. If you select this setting, you will be able to tell your iPhone how much history you want.
2 weeks, 1 month, 3 months, 6 months, All events. Your choice.
Hope this helps!