Local Daylight Time - Home

Home
About
- The Idea
- The Math
- Links
FAQ
Software
- Server API
Images
- Graphs
- 3D Earth
Contact
Local Daylight Time
- Local Daylight Time (LDT) is a smart clock that knows what time it should be. The LDT smart clock adjusts for the position of the sun at every location and date. Conventional clocks use the Standard Time system created by railroads in 1847 and then endlessly redefined by governments around the world. The result is a hodgepodge of arbitrary boundaries and clock changes based on an artificial sun.
  
  Local Daylight Time has no time zone boundaries, and it ends the hassle and jet lag of changing clocks twice a year. Local Daylight Time varies continuously with location and changes gradually, never jumping to the next hour. As the seasons change, small automatic adjustments of up to one minute per day reduce sunrise variation year round, extending summer evening daylight without the disruption of Daylight Saving Time changes.
  
  Local Daylight Time is ideal for local purposes, such as getting up and going to work. The consistent sunrise time keeps circadian rhythms natural and undisturbed, with proven health benefits. LDT works in harmony with Universal Coordinated Time (UTC) which is well suited for global time over large distances. UTC works for international conference calls, satellite broadcast times and airline schedules, while Local Daylight Time keeps communities perfectly synchronized with the sun, every day, every where.
  
  Local Daylight Time varies with the date, like the sun. Change the date above to see this effect. Latitude (north or south of the equator) also affects Local Daylight Time. The length of the day changes with latitude, from constant at the equator to extremes of midnight sun near the poles. Local Daylight Time shifts smoothly, adjusting sunrise time proportionally and adding evening daylight hours without over extending. At extreme latitudes LDT follows mean solar time, so clocks track the sun even when it does not rise or set.

Hide chart

Sunrise

Daylight

Sunset

TST-MST

STD-MST

LDT-MST

LDT-STD

LDT day

Javascript Required!

General
Map
Chart

Days Step

Earliest Latest

Explore six different time keeping systems across location and date. How are they different? When is sunrise? Sunset? How do these vary with the seasons? With latitude? What does each clock say? What time should it be? Where are the time zone boundaries? Where were they originally? Are they necessary? Where is daylight saving time used and when does it change? Is that sundial correct? Does sunrise vary at the equator? How far away from the equator before the sun doesn't rise and set every day? Find the answers for yourself using this web page.

"For the natural days
are truly unequal,
though they are
commonly considered as equal
and used for a measure of time"
Isaac Newton

Tooltips explain all of the controls and calculations as you move the cursor over them. The button in the upper left opens a dialog to search the map and save your favorite locations. Changing these allows rapid comparisons of time in different places. The date can be changed easily to find the longest day, latest sunrise, or any other peak or valley in the numbers. The map center can be moved in many ways, by panning, dragging the red marker, using the hand, or changing your saved locations, shown with blue markers. Click on time zone boundaries to display links to time information. All time calculations are immediately updated by clicks or arrow keys.

© Copyright Keith Thomas 2014