Adding Google Calendar Events by Voice on Your IPhone
Although you can access Google Calendar with Safari and use the microphone function to create a new event manually, it's far easier to sync your account to your iPhone and then use Siri to add items to the Calendar app. As long as you're connected to a wireless network, iOS automatically copies to Google Calendar any new events you add to the iPhone.
Open "Settings" from the Home screen, and then scroll to and touch "Mail, Contacts, Calendars."
Touch "Add Account" and then choose "Google" as the account type. Enter your account credentials into the available fields and then touch "Next."
Toggle "Calendars" to "On" and then return to the Mail, Contacts, Calendars screen. Touch "Default Calendar" and then select your Gmail account, if necessary.
Hold down the Home button until the message "What Can I Help You With?" appears on screen.
Tell Siri what you'd like to schedule, along with the date and time of the event. For example, "Schedule a meeting with John on March 2nd at 3 p.m."
Press "Confirm" to create the new event, or, if the information is incorrect, press "Cancel" and then press the microphone to repeat your request.
Connect your iPhone to a wireless hot spot and then open the Calendar app to sync your items.