Area code 781 is a significant telephone area code in the United States, serving a large portion of Massachusetts. Here are some key aspects of this area code:

Geographic Coverage and Establishment: Area code 781 is located in Massachusetts and was assigned for use starting on September 1, 1997. This area code originated from a split of the existing 617 area code. It was introduced to accommodate the growing demand for phone numbers in the state​​​​.

Overlay with Area Code 339: In 2001, area code 781 was overlaid with area code 339. This overlay means that both area codes serve the same geographic region. Overlay plans are commonly implemented in regions where there is a high demand for new phone numbers, allowing for a larger pool of numbers within the same geographical area​​.

Time Zone: Area code 781 is located in the Eastern Standard Time (EST) zone. Like most areas in the United States, it observes Daylight Saving Time, which involves adjusting the clocks forward in spring and backward in autumn to extend evening daylight during the warmer months​​.

In summary, area code 781 is vital for telecommunications in Massachusetts, particularly in and around major urban centers like Boston. Its establishment as a split from area code 617 and subsequent overlay with area code 339 reflect the evolving telecommunication needs in the region. The area code's coverage of key cities and counties and its alignment with the Eastern Time Zone are significant operational aspects.