Most likely, No. Thirty days is about the limit of reliable testing.

Go to this site and enter the serial & date of your bond and it will provide you the value.  If you have a Series "E" bond, remember to drop down the list box and change it from "EE" to "E." www.savingsbonds.gov

Go to this site, plug in the number/date of your Bond and it will provide you the current value: If you have a Series.