Separate useful context from calculations that need your real inputs.
A planting date depends on climate and frost risk. Bed capacity depends on real dimensions and spacing. Watering depends on area, rainfall and system flow. A useful guide should explain what matters, then hand the calculation to a tool that can use the values from your garden.
This also keeps the site honest. A general growing guide should not invent a precise local date, promise a harvest day or prescribe a treatment that depends on a cultivar, product label, microclimate or plant condition the website cannot see.