One of the first ways by which man learned to estimate the time was by observing the passage of the sun across the sky. Chaucer's Man of Law, for example, noted when:
. . . the shadow of each tree
Had reached a length of that same quantity
As was the body which had cast the shade;
And on this basis he conclusion made:
That on that day, and in that latitude,
The time was 10 o'clock.
Long before Chaucer's time, however, our ancestors had devised an instrument to improve the accuracy of their observations. They invented the sundial, and it served them well since the tempo of their lives was such that it was sufficient that their assessments be approximate.
The time indicated by a sundial is not "clock time". It is Local Apparent Time or LAT - local because it applies only at that particular longitude, and apparent because it is based on the apparent motion of the sun across the sky. If you measure days by the sun, however, they turn out to differ in length by up to half a minute, because the Earth moves faster in its orbit at certain times of the year when it is closer to the sun than it does at others. As a consequence, the sun reaches the "noon" in November about 16 minutes earlier than it would if the days were all of equal length; in February, it is about 15 minutes late.
Nowadays we pretend that there is a fictitious sun in the sky which revolves around us at a conveniently constant rate, just equal to the average speed at which the real sun appears to move in its orbit. Time measured by this average, or mean, sun is called mean time, hence the familiar phrase Greenwich Mean Time. Mean time at our sundial is called Local Mean Time (LMT), and the difference between LMT and LAT is known as the equation of time.
The value of the equation of time for each day of the year can be easily obtained from standard tables; indeed it is sometimes displayed beside a sundial, so by applying the correction to what the sundial tells you, you arrive at Local Mean Time. And then you have to remember that life nowadays is also organised around standard time zones, so in these parts you have to add four minutes to LMT for every degree of longitude west of Greenwich to arrive at GMT, and finally you add an hour to give you Summer Time.
Perhaps it might be easier to use a clock.