Gardening and Horticulture - What is "Days to H"

On seed packages, what does the "Days to Harvest" number mean? Can I use the number to gage when to harvest? When do you start counting? I'm planting melons and corn.

Thanks

Days to harvest is merely a guide. You have to physically check to see if your crops are ready. You can peel back the husk and silk on corn and take your thumbnail and squish a kernal. If a white milky liquid comes out, they are ready. Melons, all I know is the old thumping method. Good luck.

Yep, its just a guide. Its there for a couple reasons. 1 is to let you guage when its too late in the season to plant. eg) say its 89 days to H and your "frost" date is end of September. If you plant at the end of July, the plants may be killed by frost before you can harvest anything.
Its also there because some people are impatient and will plant a variety the is ready early. Or plant all at the same time, but that ripen at different times and enjoy fresh produce all summer.

Thanks for the clarification.