This is a very good question. Our 3 eyases hatched on 5/5, 5/6 and 5/7. The average from hatch to fledge is 42-44 days. So, going from the first hatch on 5/5, today is the 35th day since hatching. That means that they should start fledging around 6/16-6/18, which is next Tuesday-Thursday. Of course it's not an exact science and we know that the boys will probably fledge before the much larger/heavier Cadence (female).
Does someone want to check my math?

You can also calculate a fledge date by comparing this year to last year.
Last year, the first egg was laid on April 8. This year it was March 27, a difference of 12 days.
Last year, the first egg hatched on May 17. This year it was May 5, a difference of 12 days.
Last year, the first eyas (a male) fledged on June 26. A difference of 12 days puts this year's first fledge on June 14.