Standard Daylight Saving Time

Daylight Saving Time Rules

In the United States, the difference between Standard Time and Daylight Saving Time (DST) is primarily related to the adjustment of the clocks to make better use of daylight during certain periods of the year. Here’s a breakdown:

Standard Time

• Definition: Standard Time refers to the time zones as defined without any adjustments for daylight saving.
• Time Zones: The U.S. is divided into several time zones including Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), and Pacific Standard Time (PST).
• Usage Period: Typically observed from the first Sunday in November to the second Sunday in March.
  

  Indiana University | Monroe County

Daylight Saving Time (DST)

• Definition: Daylight Saving Time involves setting the clock forward by one hour from Standard Time to extend evening daylight.
• Adjustment: During DST, time zones are referred to as Eastern Daylight Time (EDT), Central Daylight Time (CDT), Mountain Daylight Time (MDT), and Pacific Daylight Time (PDT).
• Usage Period: Generally observed from the second Sunday in March to the first Sunday in November.
• Purpose: The main goal is to make better use of daylight during the longer days of spring, summer, and early fall, thereby conserving energy and allowing for more daylight in the evening hours.

University of Wisconsin Eau Claire

Key Differences

• Clock Adjustment: Clocks are set forward by one hour in the spring for DST and set back by one hour in the fall when reverting to Standard Time.
• Impact on Time: During DST, the time is one hour ahead of Standard Time. For example, when it is 2 PM EST (Standard Time), it would be 3 PM EDT (Daylight Saving Time).
• Daylight Utilization: DST provides an extra hour of daylight in the evening, which can be beneficial for activities after work or school and can help reduce electricity usage.

Example

• Eastern Standard Time (EST): If it is 12:00 PM (noon) EST in New York during the winter, it is 12:00 PM.
• Eastern Daylight Time (EDT): If it is 12:00 PM (noon) in New York during the summer, the actual solar time is 11:00 AM, but the clock shows 12:00 PM due to the one-hour forward adjustment for DST.

Campus Clocks