Sun Dial Time Corrections

Corrections need to be made in order to obtain Mean time from a sundial. 

These are:

  • Correction for the Equation of Time
  • Correction for Longitude
  • Correction for Summer Time

These are considered in turn below:

Want a little card to carry with you to help you check a sundial's displayed time at ANY Longitude or Latitude in the British Isles?  Hurry if you want one of the few remaining printed versions...

Click the picture for more details!

Click to download the Estimator

The equation of time describes the discrepancy between two kinds of solar time. These are Apparent Solar Time, which directly tracks the motion of the sun, and Mean Solar Time, which tracks a fictitious "mean" sun with noons 24 hours apart. Apparent (or true) solar time is that indicated by a sundial. Mean solar time, for the same place, would be the time indicated by a steady clock set so that over the year its differences from apparent solar time average to zero. Why not get The Recorder's Reference? It provides anyone interested in dialling with a way to estimate by how much a non-direct-south vertical dial declines and also finds the design latitude for any horizontal dial. 

Click the picture for more details!

I - Equation of Time Correction - 2017 & 2016 (Still want corrections for 2015?)
This page P.Powers 2013, 2014, 2015, 2016, 2017 All Rights Reserved

The figures in the tables below show more accurate figures in mins and secs by which a sundial should be corrected during the whole of 2016 and 2017.  A link is also included to a printable page of the 2015 EoT figures. The figures in the tables represent the Equation of Time at 12Hrs (Noon) GMT on the date stated and are here calculated using the method after Smart (1956) which is accurate at worst to about 4 secs - frequently to one second..  Interpolation will of course, be necessary if an EoT is needed for times other than Noon. Note that in non-leap-years there is still an entry in the tables for Feb 29th but its value is then the same as that for Mar 1st. NB Don't forget the two other corrections...

Negative values in the table indicate Dial Slow.

Equation of Time Correction - 2017 & 2016
2017 One Page Printable version of 2017 EoT 2016 One Page Printable version of 2016 EoT
Jan-01 -3m 41s   May-01 2m 56s   Sep-01 0m 3s
Jan-02 -4m 8s   May-02 3m 2s   Sep-02 0m 22s
Jan-03 -4m 36s   May-03 3m 8s   Sep-03 0m 42s
Jan-04 -5m 3s   May-04 3m 14s   Sep-04 1m 2s
Jan-05 -5m 30s   May-05 3m 19s   Sep-05 1m 22s
Jan-06 -5m 56s   May-06 3m 24s   Sep-06 1m 42s
Jan-07 -6m 22s   May-07 3m 28s   Sep-07 2m 2s
Jan-08 -6m 48s   May-08 3m 31s   Sep-08 2m 23s
Jan-09 -7m 13s   May-09 3m 34s   Sep-09 2m 44s
Jan-10 -7m 37s   May-10 3m 36s   Sep-10 3m 4s
Jan-11 -8m 1s   May-11 3m 38s   Sep-11 3m 25s
Jan-12 -8m 24s   May-12 3m 39s   Sep-12 3m 47s
Jan-13 -8m 46s   May-13 3m 39s   Sep-13 4m 8s
Jan-14 -9m 8s   May-14 3m 39s   Sep-14 4m 29s
Jan-15 -9m 30s   May-15 3m 38s   Sep-15 4m 51s
Jan-16 -9m 50s   May-16 3m 37s   Sep-16 5m 12s
Jan-17 -10m 10s   May-17 3m 36s   Sep-17 5m 33s
Jan-18 -10m 29s   May-18 3m 33s   Sep-18 5m 55s
Jan-19 -10m 48s   May-19 3m 30s   Sep-19 6m 16s
Jan-20 -11m 6s   May-20 3m 27s   Sep-20 6m 38s
Jan-21 -11m 23s   May-21 3m 23s   Sep-21 6m 59s
Jan-22 -11m 39s   May-22 3m 19s   Sep-22 7m 20s
Jan-23 -11m 54s   May-23 3m 14s   Sep-23 7m 41s
Jan-24 -12m 9s   May-24 3m 8s   Sep-24 8m 2s
Jan-25 -12m 23s   May-25 3m 2s   Sep-25 8m 23s
Jan-26 -12m 36s   May-26 2m 56s   Sep-26 8m 44s
Jan-27 -12m 48s   May-27 2m 49s   Sep-27 9m 4s
Jan-28 -12m 60s   May-28 2m 41s   Sep-28 9m 24s
Jan-29 -13m 10s   May-29 2m 33s   Sep-29 9m 44s
Jan-30 -13m 20s   May-30 2m 25s   Sep-30 10m 4s
Jan-31 -13m 29s   May-31 2m 16s   Oct-01 10m 24s
Feb-01 -13m 37s   Jun-01 2m 7s   Oct-02 10m 43s
Feb-02 -13m 45s   Jun-02 1m 58s   Oct-03 11m 2s
Feb-03 -13m 51s   Jun-03 1m 48s   Oct-04 11m 20s
Feb-04 -13m 57s   Jun-04 1m 38s   Oct-05 11m 39s
Feb-05 -14m 2s   Jun-05 1m 27s   Oct-06 11m 56s
Feb-06 -14m 6s   Jun-06 1m 16s   Oct-07 12m 14s
Feb-07 -14m 9s   Jun-07 1m 5s   Oct-08 12m 31s
Feb-08 -14m 12s   Jun-08 0m 53s   Oct-09 12m 48s
Feb-09 -14m 14s   Jun-09 0m 42s   Oct-10 13m 4s
Feb-10 -14m 14s   Jun-10 0m 30s   Oct-11 13m 20s
Feb-11 -14m 15s   Jun-11 0m 18s   Oct-12 13m 35s
Feb-12 -14m 14s   Jun-12 0m 5s   Oct-13 13m 49s
Feb-13 -14m 12s   Jun-13 -0m 7s   Oct-14 14m 4s
Feb-14 -14m 10s   Jun-14 -0m 20s   Oct-15 14m 17s
Feb-15 -14m 7s   Jun-15 -0m 33s   Oct-16 14m 30s
Feb-16 -14m 4s   Jun-16 -0m 46s   Oct-17 14m 43s
Feb-17 -13m 59s   Jun-17 -0m 59s   Oct-18 14m 55s
Feb-18 -13m 54s   Jun-18 -1m 12s   Oct-19 15m 6s
Feb-19 -13m 49s   Jun-19 -1m 25s   Oct-20 15m 16s
Feb-20 -13m 42s   Jun-20 -1m 38s   Oct-21 15m 26s
Feb-21 -13m 35s   Jun-21 -1m 51s   Oct-22 15m 36s
Feb-22 -13m 28s   Jun-22 -2m 4s   Oct-23 15m 44s
Feb-23 -13m 19s   Jun-23 -2m 17s   Oct-24 15m 52s
Feb-24 -13m 10s   Jun-24 -2m 30s   Oct-25 15m 59s
Feb-25 -13m 1s   Jun-25 -2m 42s   Oct-26 16m 6s
Feb-26 -12m 51s   Jun-26 -2m 55s   Oct-27 16m 11s
Feb-27 -12m 40s   Jun-27 -3m 7s   Oct-28 16m 16s
Feb-28 -12m 29s   Jun-28 -3m 20s   Oct-29 16m 20s
Feb-29 -12m 17s   Jun-29 -3m 32s   Oct-30 16m 24s
Mar-01 -12m 17s   Jun-30 -3m 44s   Oct-31 16m 26s
Mar-02 -12m 5s   Jul-01 -3m 55s   Nov-01 16m 28s
Mar-03 -11m 52s   Jul-02 -4m 7s   Nov-02 16m 29s
Mar-04 -11m 39s   Jul-03 -4m 18s   Nov-03 16m 29s
Mar-05 -11m 26s   Jul-04 -4m 28s   Nov-04 16m 28s
Mar-06 -11m 12s   Jul-05 -4m 39s   Nov-05 16m 27s
Mar-07 -10m 57s   Jul-06 -4m 49s   Nov-06 16m 24s
Mar-08 -10m 42s   Jul-07 -4m 59s   Nov-07 16m 21s
Mar-09 -10m 27s   Jul-08 -5m 8s   Nov-08 16m 17s
Mar-10 -10m 12s   Jul-09 -5m 17s   Nov-09 16m 12s
Mar-11 -9m 56s   Jul-10 -5m 25s   Nov-10 16m 6s
Mar-12 -9m 40s   Jul-11 -5m 33s   Nov-11 15m 60s
Mar-13 -9m 24s   Jul-12 -5m 41s   Nov-12 15m 52s
Mar-14 -9m 7s   Jul-13 -5m 48s   Nov-13 15m 44s
Mar-15 -8m 50s   Jul-14 -5m 55s   Nov-14 15m 34s
Mar-16 -8m 33s   Jul-15 -6m 1s   Nov-15 15m 24s
Mar-17 -8m 16s   Jul-16 -6m 7s   Nov-16 15m 13s
Mar-18 -7m 58s   Jul-17 -6m 12s   Nov-17 15m 1s
Mar-19 -7m 41s   Jul-18 -6m 16s   Nov-18 14m 49s
Mar-20 -7m 23s   Jul-19 -6m 20s   Nov-19 14m 35s
Mar-21 -7m 5s   Jul-20 -6m 24s   Nov-20 14m 21s
Mar-22 -6m 47s   Jul-21 -6m 27s   Nov-21 14m 6s
Mar-23 -6m 29s   Jul-22 -6m 29s   Nov-22 13m 50s
Mar-24 -6m 11s   Jul-23 -6m 31s   Nov-23 13m 33s
Mar-25 -5m 53s   Jul-24 -6m 32s   Nov-24 13m 16s
Mar-26 -5m 35s   Jul-25 -6m 33s   Nov-25 12m 58s
Mar-27 -5m 17s   Jul-26 -6m 33s   Nov-26 12m 39s
Mar-28 -4m 59s   Jul-27 -6m 32s   Nov-27 12m 19s
Mar-29 -4m 41s   Jul-28 -6m 31s   Nov-28 11m 58s
Mar-30 -4m 23s   Jul-29 -6m 29s   Nov-29 11m 37s
Mar-31 -4m 5s   Jul-30 -6m 27s   Nov-30 11m 16s
Apr-01 -3m 47s   Jul-31 -6m 24s   Dec-01 10m 53s
Apr-02 -3m 29s   Aug-01 -6m 20s   Dec-02 10m 30s
Apr-03 -3m 12s   Aug-02 -6m 16s   Dec-03 10m 6s
Apr-04 -2m 54s   Aug-03 -6m 11s   Dec-04 9m 42s
Apr-05 -2m 37s   Aug-04 -6m 5s   Dec-05 9m 17s
Apr-06 -2m 20s   Aug-05 -5m 59s   Dec-06 8m 52s
Apr-07 -2m 3s   Aug-06 -5m 53s   Dec-07 8m 26s
Apr-08 -1m 47s   Aug-07 -5m 45s   Dec-08 8m 0s
Apr-09 -1m 30s   Aug-08 -5m 38s   Dec-09 7m 33s
Apr-10 -1m 14s   Aug-09 -5m 29s   Dec-10 7m 6s
Apr-11 -0m 59s   Aug-10 -5m 20s   Dec-11 6m 39s
Apr-12 -0m 43s   Aug-11 -5m 11s   Dec-12 6m 11s
Apr-13 -0m 28s   Aug-12 -5m 1s   Dec-13 5m 42s
Apr-14 -0m 13s   Aug-13 -4m 50s   Dec-14 5m 14s
Apr-15 0m 1s   Aug-14 -4m 39s   Dec-15 4m 45s
Apr-16 0m 16s   Aug-15 -4m 27s   Dec-16 4m 16s
Apr-17 0m 29s   Aug-16 -4m 15s   Dec-17 3m 47s
Apr-18 0m 43s   Aug-17 -4m 2s   Dec-18 3m 17s
Apr-19 0m 56s   Aug-18 -3m 49s   Dec-19 2m 48s
Apr-20 1m 8s   Aug-19 -3m 35s   Dec-20 2m 18s
Apr-21 1m 20s   Aug-20 -3m 21s   Dec-21 1m 49s
Apr-22 1m 32s   Aug-21 -3m 6s   Dec-22 1m 19s
Apr-23 1m 43s   Aug-22 -2m 51s   Dec-23 0m 49s
Apr-24 1m 54s   Aug-23 -2m 35s   Dec-24 0m 19s
Apr-25 2m 4s   Aug-24 -2m 19s   Dec-25 -0m 10s
Apr-26 2m 14s   Aug-25 -2m 3s   Dec-26 -0m 40s
Apr-27 2m 24s   Aug-26 -1m 46s   Dec-27 -1m 9s
Apr-28 2m 32s   Aug-27 -1m 28s   Dec-28 -1m 39s
Apr-29 2m 41s   Aug-28 -1m 11s   Dec-29 -2m 8s
Apr-30 2m 48s   Aug-29 -0m 53s   Dec-30 -2m 37s
      Aug-30 -0m 35s   Dec-31 -3m 5s
      Aug-31 -0m 16s      
Jan-01 -3m 19s   May-01 2m 57s   Sep-01 0m 8s
Jan-02 -3m 47s   May-02 3m 4s   Sep-02 0m 27s
Jan-03 -4m 15s   May-03 3m 10s   Sep-03 0m 47s
Jan-04 -4m 43s   May-04 3m 15s   Sep-04 1m 6s
Jan-05 -5m 10s   May-05 3m 20s   Sep-05 1m 26s
Jan-06 -5m 37s   May-06 3m 25s   Sep-06 1m 47s
Jan-07 -6m 3s   May-07 3m 28s   Sep-07 2m 7s
Jan-08 -6m 29s   May-08 3m 32s   Sep-08 2m 28s
Jan-09 -6m 54s   May-09 3m 34s   Sep-09 2m 49s
Jan-10 -7m 19s   May-10 3m 36s   Sep-10 3m 10s
Jan-11 -7m 43s   May-11 3m 38s   Sep-11 3m 31s
Jan-12 -8m 6s   May-12 3m 39s   Sep-12 3m 52s
Jan-13 -8m 30s   May-13 3m 39s   Sep-13 4m 13s
Jan-14 -8m 52s   May-14 3m 39s   Sep-14 4m 34s
Jan-15 -9m 14s   May-15 3m 38s   Sep-15 4m 56s
Jan-16 -9m 35s   May-16 3m 37s   Sep-16 5m 17s
Jan-17 -9m 55s   May-17 3m 35s   Sep-17 5m 39s
Jan-18 -10m 15s   May-18 3m 33s   Sep-18 5m 60s
Jan-19 -10m 34s   May-19 3m 30s   Sep-19 6m 21s
Jan-20 -10m 52s   May-20 3m 26s   Sep-20 6m 43s
Jan-21 -11m 10s   May-21 3m 22s   Sep-21 7m 4s
Jan-22 -11m 27s   May-22 3m 17s   Sep-22 7m 25s
Jan-23 -11m 43s   May-23 3m 12s   Sep-23 7m 46s
Jan-24 -11m 58s   May-24 3m 7s   Sep-24 8m 7s
Jan-25 -12m 13s   May-25 3m 1s   Sep-25 8m 28s
Jan-26 -12m 26s   May-26 2m 54s   Sep-26 8m 49s
Jan-27 -12m 39s   May-27 2m 47s   Sep-27 9m 9s
Jan-28 -12m 51s   May-28 2m 39s   Sep-28 9m 29s
Jan-29 -13m 3s   May-29 2m 32s   Sep-29 9m 49s
Jan-30 -13m 13s   May-30 2m 23s   Sep-30 10m 9s
Jan-31 -13m 23s   May-31 2m 14s   Oct-01 10m 28s
Feb-01 -13m 31s   Jun-01 2m 5s   Oct-02 10m 47s
Feb-02 -13m 39s   Jun-02 1m 55s   Oct-03 11m 6s
Feb-03 -13m 47s   Jun-03 1m 46s   Oct-04 11m 25s
Feb-04 -13m 53s   Jun-04 1m 35s   Oct-05 11m 43s
Feb-05 -13m 58s   Jun-05 1m 25s   Oct-06 12m 1s
Feb-06 -14m 3s   Jun-06 1m 14s   Oct-07 12m 18s
Feb-07 -14m 7s   Jun-07 1m 2s   Oct-08 12m 35s
Feb-08 -14m 10s   Jun-08 0m 51s   Oct-09 12m 52s
Feb-09 -14m 12s   Jun-09 0m 39s   Oct-10 13m 8s
Feb-10 -14m 14s   Jun-10 0m 27s   Oct-11 13m 23s
Feb-11 -14m 15s   Jun-11 0m 15s   Oct-12 13m 38s
Feb-12 -14m 15s   Jun-12 0m 2s   Oct-13 13m 53s
Feb-13 -14m 14s   Jun-13 -0m 10s   Oct-14 14m 7s
Feb-14 -14m 12s   Jun-14 -0m 23s   Oct-15 14m 20s
Feb-15 -14m 10s   Jun-15 -0m 36s   Oct-16 14m 33s
Feb-16 -14m 7s   Jun-16 -0m 49s   Oct-17 14m 46s
Feb-17 -14m 3s   Jun-17 -1m 2s   Oct-18 14m 57s
Feb-18 -13m 58s   Jun-18 -1m 15s   Oct-19 15m 8s
Feb-19 -13m 53s   Jun-19 -1m 28s   Oct-20 15m 19s
Feb-20 -13m 47s   Jun-20 -1m 41s   Oct-21 15m 29s
Feb-21 -13m 41s   Jun-21 -1m 54s   Oct-22 15m 38s
Feb-22 -13m 34s   Jun-22 -2m 7s   Oct-23 15m 46s
Feb-23 -13m 26s   Jun-23 -2m 20s   Oct-24 15m 54s
Feb-24 -13m 17s   Jun-24 -2m 32s   Oct-25 16m 1s
Feb-25 -13m 8s   Jun-25 -2m 45s   Oct-26 16m 7s
Feb-26 -12m 59s   Jun-26 -2m 58s   Oct-27 16m 13s
Feb-27 -12m 48s   Jun-27 -3m 10s   Oct-28 16m 17s
Feb-28 -12m 38s   Jun-28 -3m 22s   Oct-29 16m 21s
Feb-29 -12m 26s   Jun-29 -3m 34s   Oct-30 16m 24s
Mar-01 -12m 14s   Jun-30 -3m 46s   Oct-31 16m 27s
Mar-02 -12m 2s   Jul-01 -3m 58s   Nov-01 16m 28s
Mar-03 -11m 49s   Jul-02 -4m 9s   Nov-02 16m 29s
Mar-04 -11m 36s   Jul-03 -4m 20s   Nov-03 16m 29s
Mar-05 -11m 22s   Jul-04 -4m 31s   Nov-04 16m 28s
Mar-06 -11m 8s   Jul-05 -4m 41s   Nov-05 16m 26s
Mar-07 -10m 54s   Jul-06 -4m 51s   Nov-06 16m 24s
Mar-08 -10m 39s   Jul-07 -5m 1s   Nov-07 16m 20s
Mar-09 -10m 24s   Jul-08 -5m 10s   Nov-08 16m 16s
Mar-10 -10m 8s   Jul-09 -5m 19s   Nov-09 16m 11s
Mar-11 -9m 52s   Jul-10 -5m 27s   Nov-10 16m 5s
Mar-12 -9m 36s   Jul-11 -5m 35s   Nov-11 15m 58s
Mar-13 -9m 20s   Jul-12 -5m 43s   Nov-12 15m 50s
Mar-14 -9m 3s   Jul-13 -5m 50s   Nov-13 15m 41s
Mar-15 -8m 46s   Jul-14 -5m 56s   Nov-14 15m 32s
Mar-16 -8m 29s   Jul-15 -6m 2s   Nov-15 15m 22s
Mar-17 -8m 12s   Jul-16 -6m 8s   Nov-16 15m 10s
Mar-18 -7m 54s   Jul-17 -6m 13s   Nov-17 14m 58s
Mar-19 -7m 36s   Jul-18 -6m 17s   Nov-18 14m 45s
Mar-20 -7m 19s   Jul-19 -6m 21s   Nov-19 14m 32s
Mar-21 -7m 1s   Jul-20 -6m 24s   Nov-20 14m 17s
Mar-22 -6m 43s   Jul-21 -6m 27s   Nov-21 14m 2s
Mar-23 -6m 25s   Jul-22 -6m 29s   Nov-22 13m 46s
Mar-24 -6m 7s   Jul-23 -6m 31s   Nov-23 13m 29s
Mar-25 -5m 49s   Jul-24 -6m 32s   Nov-24 13m 11s
Mar-26 -5m 30s   Jul-25 -6m 33s   Nov-25 12m 53s
Mar-27 -5m 12s   Jul-26 -6m 32s   Nov-26 12m 34s
Mar-28 -4m 54s   Jul-27 -6m 32s   Nov-27 12m 14s
Mar-29 -4m 36s   Jul-28 -6m 30s   Nov-28 11m 53s
Mar-30 -4m 18s   Jul-29 -6m 28s   Nov-29 11m 32s
Mar-31 -4m 0s   Jul-30 -6m 26s   Nov-30 11m 10s
Apr-01 -3m 43s   Jul-31 -6m 23s   Dec-01 10m 48s
Apr-02 -3m 25s   Aug-01 -6m 19s   Dec-02 10m 24s
Apr-03 -3m 7s   Aug-02 -6m 14s   Dec-03 10m 1s
Apr-04 -2m 50s   Aug-03 -6m 9s   Dec-04 9m 36s
Apr-05 -2m 33s   Aug-04 -6m 4s   Dec-05 9m 11s
Apr-06 -2m 16s   Aug-05 -5m 58s   Dec-06 8m 46s
Apr-07 -1m 59s   Aug-06 -5m 51s   Dec-07 8m 20s
Apr-08 -1m 43s   Aug-07 -5m 44s   Dec-08 7m 53s
Apr-09 -1m 26s   Aug-08 -5m 36s   Dec-09 7m 27s
Apr-10 -1m 10s   Aug-09 -5m 27s   Dec-10 6m 59s
Apr-11 -0m 55s   Aug-10 -5m 18s   Dec-11 6m 32s
Apr-12 -0m 39s   Aug-11 -5m 8s   Dec-12 6m 4s
Apr-13 -0m 24s   Aug-12 -4m 58s   Dec-13 5m 35s
Apr-14 -0m 9s   Aug-13 -4m 47s   Dec-14 5m 7s
Apr-15 0m 5s   Aug-14 -4m 36s   Dec-15 4m 38s
Apr-16 0m 19s   Aug-15 -4m 24s   Dec-16 4m 9s
Apr-17 0m 33s   Aug-16 -4m 12s   Dec-17 3m 40s
Apr-18 0m 46s   Aug-17 -3m 59s   Dec-18 3m 10s
Apr-19 0m 59s   Aug-18 -3m 45s   Dec-19 2m 41s
Apr-20 1m 11s   Aug-19 -3m 31s   Dec-20 2m 11s
Apr-21 1m 23s   Aug-20 -3m 17s   Dec-21 1m 41s
Apr-22 1m 35s   Aug-21 -3m 2s   Dec-22 1m 11s
Apr-23 1m 46s   Aug-22 -2m 47s   Dec-23 0m 42s
Apr-24 1m 57s   Aug-23 -2m 31s   Dec-24 0m 12s
Apr-25 2m 7s   Aug-24 -2m 15s   Dec-25 -0m 18s
Apr-26 2m 17s   Aug-25 -1m 58s   Dec-26 -0m 47s
Apr-27 2m 26s   Aug-26 -1m 41s   Dec-27 -1m 17s
Apr-28 2m 34s   Aug-27 -1m 24s   Dec-28 -1m 46s
Apr-29 2m 43s   Aug-28 -1m 6s   Dec-29 -2m 15s
Apr-30 2m 50s   Aug-29 -0m 48s   Dec-30 -2m 44s
      Aug-30 -0m 30s   Dec-31 -3m 12s
      Aug-31 -0m 11s      


Negative values in the table indicate Dial Slow.  

Accuracy - Just how accurate are these estimates of EoT?
The above EoT figures are calculated using Meeus's 'simpler' formula (after Smart) and are generally accurate to within 4 seconds and to less than 1 second for most of the year.
To illustrate this, the graph below shows the errors in seconds of Smart's EoT figures for 2012 when a detailed comparison was last made.

II - Correction for Longitude

When a dial is not on the local Time Meridian, for example for a dial in the UK that is not on the actual Greenwich Meridian, then the sun is overhead at the dial at a time earlier or later than at Greenwich.  The correction to be made is 4 minutes of time for every degree of longitude difference from Greenwich.  This figure should be subtracted from the dial reading for dials East of Greenwich (such dials are Fast) and added for dials West of Greenwich. (such dials are Slow).

III - Correction for Summer Time

Lastly during the period when Summer Time (Daylight Saving Time) is in force one hour should be added to the corrected sundial reading to obtain clock time.

Finally, how about a simple in-the-pocket card that allows you to check a dial at any Latitude or Longitude in the British Isles, by converting its Solar time to Clock time?

Click on the image below to find out how!

Click to download the Estimator


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