Apparent solar Time or Apparent Time is the most obvious measurement of time for an observer on the surface of the earth.
It is a system based on the observation of the sun position in the sky. The sun appears to describe a 360º circle around the earth.
For the observer the sun will change position 15º/h (360º/24h).

LMTs difference = change longitude / 15

Local Mean Time is obtain determining at the local apparent noon at specific meridian.
Local noon occurs at the same local time at all altitudes of the same meridian.
Local Mean Time is inappropriate for use in a country as a standard time. Countries with cities with different longitudes, would have different LMT’s.

Standard Time is the convention where clocks within a geographical region are synchronized to a single time standard.
Each country defines its own Standard Time notified in the Air Almanac of its correction related to UTC.
Each country tries to fix 1200 ST to occur at half period of light and 2400 ST to occur half of period of darkness.

Universal Coordinated time (UTC) is the primary global standard time.
To avoid confusions with different time zones and daylight saving time, UTC is the time used in aviation for air traffic control services, clearances, flight plans and weather forecast.

It is often necessary convert LMT to UTC and vice-versa. Based on apparent movement of the sun from east to west:

Longitude east, UTC is least
Longitude west, UTC is best

Summer Time / Daylight Saving Time is adopted in some countries within the summer months.
Those are identified with an * in the Air Almanac. Summer Time is normally advanced 1 hour in advanced to Standard Time.

1º - Determine the LMT for the evening civil twilight at 68º58ºN.

As the table does not provide the 18 November and 69º N, you will need to interpolate the values between 16 and 19 November, as well the values between 68º and 70º N.

2º - Convert the 1515 LMT to UTC:

Time difference = 35º05’ / 15 = 2º20’

Longitude east, 15º15’ - 2º20’ = 12º55’ UTC