osx - applescript pausing randomly

I have the following code. Using the keystroke to type out the item in the list however it seems like at times it randomly misses characters when running or gets stuck one random characters. Almost like the script it too fast for the os. running a MacBook pro with i7. how can i make sure that the script in questions below doesn’t miss characters or any script. seems to happen with the keystroke implementation. Are there any other ways??

set startDate to {"Dec 1, 2015", "Jan 1, 2016", "Feb 1, 2016", "Mar 1, 2016", "Apr 1, 2016", "May 1, 2016", "Jun 1, 2016", "Jul 1, 2016", "Aug 1, 2016", "Sep 1, 2016", "Oct 1, 2016", "Nov 1, 2016"}
set endDate to {"Dec 31, 2015", "Jan 31, 2016", "Feb 29, 2016", "Mar 31, 2016", "Apr 30, 2016", "May 31, 2016", "Jun 30, 2016", "Jul 31, 2016", "Aug 31, 2016", "Sep 30, 2016", "Oct 31, 2016", "Nov 30, 2016"}

tell application "System Events"
	delay 1
	keystroke "a" using command down
	keystroke item 1 of startDate
	delay 1
	keystroke tab
	keystroke item 1 of endDate
	delay 1
	keystroke tab
end tell

thanks,

Just a suggestion, not sure it helps, but it’s better to target the process than using the Global/System Events scope.

tell application "System Events"
	tell process "Microsoft Word"
		delay 1
		keystroke "a" using command down
		keystroke item 1 of startDate
		delay 1
		keystroke tab
		keystroke item 1 of endDate
		delay 1
		keystroke tab
	end tell
end tell

thanks greatly appreciate it! it looks like it might do it. seems to much more quicker and accurate in the initially testing. I’ll keep an eye on it to make sure.