The change in Local Mean Time is equal to 4 minutes per degree of longitude.

Therefore:

090°W to 000° E/W = 090° x 4 = 360 minute = 12 hours. Greenwich Meridian is East of 090°W, therefore ADD the time difference. 1400 + 6 = 2000 LMT.

090°W to 090°E = 180° x 4 = 720 minute = 12 hours. 090°E is East of 090°W, therefore ADD the time difference. 1400 + 12 = 0200 LMT.

090°W to 120°W = 030° x 4 = 120 minute = 2 hours. 120°W is West of 090°W, therefore SUBTRACT the time difference. 1400 - 2 = 1200 LMT.

090°W to 060°W = 030° x 4 = 120 minute = 2 hours. 060°W is East of 090°W, therefore ADD the time difference. 1400 + 2 = 1600 LMT.