CalendarCosmos
Print calendars and track holidays and astronomy dates
stopwatchpro.app
Online stopwatch and interval timer with laps and workout history
StopwatchPro provides millisecond-precision timing, lap tracking, and HIIT or Tabata interval presets. It also includes audio cues, countdown timing, and automatic session history with analytics.
Athletes and coaches timing workouts.
StopwatchPro is an independent website. Tools Lib lists it; features and pricing are set by its makers and can change.