5.4. Scenario 3 – continuous 30 minutes forward with single DST from April to October
This option has been designed to offset the summer disadvantages in Scenario 2 (continuous 30 minutes forward). According to this scenario, the time is shifted forward by 30 minutes as in Scenario 2 and DST takes effect on the same dates (from April to October) as in the status quo. Therefore, Turkey stays in the GMT+2.5 time zone in winter and in the GMT+3.5 time zone during DST months. The starting and ending dates of DST remains the same as in the EU countries.
Possible gains and losses for Istanbul between the months of November and March were discussed in Scenario 2. When compared to the status quo, daylight will be used 30 minutes more from April to October. When compared to Scenario 2, daylight will be used 1 hour more from April to October, which would prevent the summer losses in Scenario 2. Relative error is reduced to 4.67%, compared to the 4.99% of the status quo.
There is no daylight loss problem mentioned for Erzurum between November-March. However, in Scenario 2, a 30-minute loss occurs between April and October. In this third scenario, not only will this 30-minute loss be eliminated, but also there will be an additional 30-minute daylight gain. Relative error is reduced to 6.48%, compared to the 10.25% of the status quo and the 10.78% of scenario 2.
5.5. Scenario 4 – continuous DST with double DST from April to October
This scenario presumes that clocks are not moved backward but forward between April and October. Turkey will be in the GMT+3 time zone during winter months of November to March and in the GMT+4 time zone from April to October. The clocks will be the same as in Scenario 1 in winter months. Therefore, Turkey will be 1 hour ahead of the status quo throughout the year in this scenario.
The advantages and disadvantages of continuous DST for Istanbul between November and March were discussed in Scenario 1. There will be 20 minutes darkness in April, 11 minutes in August, 40 minutes in September, and 1 hour 12 minutes in October. Sunset in the summer will be at 21:30 on average, which may have an adverse effect on people resting throughout the evening. Relative error is increased to 6.11%, compared to the 4.67% of Scenario 3.
The application between November and March will be the same as in Scenario 1. Therefore, advantages and disadvantages will be similar. When the time between April and October is considered, there will be morning darkness only in October for 22 minutes. Sunset times will range between 19:26 (September) and 20:48 (June), which would not lead to any problems, as current sunset times are similar in western cities. Relative error will be 4.21%.
5.6. Scenario 5 – maintaining the status quo by changing DST dates
In this scenario, winter and summer time shifts will be the same as in the status quo. The only difference between this alternative and the status quo is the different start and end times for DST. According to this, the existing dates will have to be extended. The practice that currently starts in the last week of March will be initiated on the first Sunday of March. While it currently ends on the last Sunday of October, it will be extended for one week to the first Sunday of November, as is the case in the USA. This scenario is similar to the status quo considering the advantages and disadvantages except the month of March. When the practice starts 3 weeks earlier in Istanbul, the Sun will rise at 7:09 on average, causing 9 minutes of darkness in March. Relative error in this scenario is 4.52%. The scenario would cause no morning darkness in Erzurum. Relative error is 9.56%.