Nectar flows are very, very variable, depending on region and weather.
Each year the nectar flow is different in intensity and starting and finishing at different dates. It'd be very hard to make a calendar that was useful every year.
I guess that as more beekeepers use scales, we could start carrying average values from year to year.
But for example, this year, the nectar flow started much earlier and it was longer in our yard.
We have some scales at the BeeManiacs yard, so we can track when they collect nectar and when the nectar flow stops or slows down.
But you can also tell by "reading" your colonies while inspecting or even honey bee behavior.
Please take a look at this other post we made about 10 days ago, about nectar flow stopping in our area:
I just moved a little farther north of you up by Loon Lake is there anyone up in that area that I may be able to talk to?
The bummer part is I'm working over in Seattle and we don't leave Seattle until 5:30 at night on Thursdays