Contact
Found a number that looks wrong, want a tool added, or interested in sponsoring the site? Send an email.
Reporting a calculation problem
Include the tool, the values you entered and the result you expected. For the planner and calendar, your latitude, longitude, time zone and date help most. Every tool page lists its formulas under Method, so you can point to the step that looks off.
Sponsorship
Tool pages have ad slots that can carry a direct sponsor's image and link instead of Google ads. Email for sizes and rates.