While I won't directly comment on why daylight savings was created, and how it's still justified today, there is an ongoing concern of how daylight savings time affects those of us that regularly work across time zones. Especially in an increasingly connected world, it's easier than ever to work across borders and seas with little interrupt. In fact, technology has made the task of tracking daylight savings time significantly easier.
I regularly have meetings with counterparts across the global, most specifically in India. Since India is almost a full 12 hours across the globe, a typical meeting time for us is early US morning, late India evening. Culturally I found in my own visit to Mumbai that most workers that work with colleagues across the globe don't show up to work until 10AM or even later, and work later into the evening to better accommodate the time zone changes.
Time Zones 101
The mainland US has four separate time zones, pacific, mountain, central, and eastern time. Each zone is +1 hour from each other, starting with pacific time on the West coast. Coordinated Universal Time (UTC) is a commonly used timescale to understand how time zones differ from each other in a relative sense. More on this later.
Here's a simple visualization of the US mainland four time zones:
Drawing a vertical line through any time will show you the equivalent time in a different time zone. Daylight savings is also pretty straight forward across the US. "Spring forward, fall back" is an easy way to remember the change. For example, in 2019, daylight savings will start on March 10th, and end on November 3rd.
Daylight Savings (in the US)
Daylight savings is intended to provide an extra hour of sunset light, although you do sacrifice an hour of sleep when it starts. You gain that hour back when daylight savings times ends:
How Daylight Savings Affects Other Time Zones
Like with currency, everyone has some "base" time zone. One that you are most likely to compare all other time zones against. For example, the UK is 6 hours ahead of Kansas (Central Time). The "frame" here is Central Time. This gets a little tricky when you consider how daylight savings affects your frame:
This simple line is meant to illustrate how regardless of how daylight savings has affected your time zone, the new times (e.g. 8AM is now 9AM) are the same to you (e.g. 8AM is still 8AM). So if daylight savings time hasn't shifted your time zone (side note that there is a difference between standard time and daylight time), it must have affected others that do not follow daylight savings conventions.
For myself, as I work with teams based in India, I follow an approximate 12 hour time change between central time and India Standard Time (IST).
In the example above, you can see that CST and CDT hasn't shifted at all (recall the frame of reference), so the additional hour needs to be accounted for in other time zones. In the case of India, since we've moved forward one hour, CDT and IST are 1 hour closer together.
The effect of this is that meetings or any scheduled event that is based on a timezone that recognizes daylight savings, then the recipient (who operate in an area that does not recognize daylight savings) will have the meeting timing adjusted accordingly.
Time Zones as Differences
Finally, another good way to visual this change is calculating changes (delta) in time between two zones. Using UTC we can look at the difference between two zones. CST to IST, for example, is 11.5 hours. Using 9AM CST as a further example, you can see that 9AM + 11.5 hours = 830PM in IST. When daylight savings starts, CST (now CDT) is one hour less, meaning the difference between these zones is now only 10.5 hours.
The same is true when daylight savings ends - that one hour difference is removed, which adds an hour between time zones.
If you work with distributed teams or persons that work across zones that do and do not utilize daylight savings, you should be aware of how this annual occurrence affects meetings.
First, be aware of the regions that recognize daylight savings:
Second, know that when daylight savings starts, when we spring forward, others have lost an hour.
And finally, when daylight savings ends, when we fall backwards, others have gained an hour. Luckily Outlook is pretty good of keeping track of this for us.
Photo Credit: Dribbble - Aleksandar Savic