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Technological progress has meant changes in the way we experience time. As historian and critic Lewis Mumford wrote, "The clock, not the steam-engine, is the key machine of the modern industrial age." In the domestic sphere, an older way of measuring time still reigns -- task-measured time, in which you do something for as long as it takes (feed a baby, cook a stew). But at work we measure time with clocks. It's no accident that a common expression for working is "being on the clock."

At the core of the changes isn't merely that we can measure time more precisely, but that we actually divide time into smaller and smaller pieces. In his landmark 1965 12-country time-diary study, German sociologist Erwin Scheuch found that the more industrialized a country became, the more activities its people crammed into a 24-hour period. He called this phenomenon time-deepening, but, as Judith Shulevitz writes in her book The Sabbath World: Glimpses of a Different Order of Time, this phrase is misleading "because stuffing life with more things and distractions makes time feel shallower, not deeper."

The Sabbath has always acted as a sort of protection from "time-deepening." In a metaphorical sense, this is true even of the prototypical Sabbath, during which God rested from the work of the first fragmentation of time -- the day from the night.

Today, time-deepening has been accelerated -- or, at least, we sense that it has been accelerated -- by changes in our economy that require more Americans to work longer hours and to be more reachable when they're at home, bringing time-deepening into our domestic sphere and interrupting our task-measured time. Shulevitz writes that, "More Americans work during the off-hours than they did half a century ago, the heyday of the nine-to-five, Monday-through-Friday workweek. According to the sociologist Harriet B. Presser, as of 2003, two-fifths of American workers were working non-standard hours -- 'in the evening, at night, on a rotating shift, or during the weekend' -- and she wasn't counting those who bring their work home and do it on their off-hours, or who are self-employed."

When we experience time-deepening we don't merely feel that we are doing more in a day; we feel that time is actually moving faster. Research into how people perceive time suggests that when people are distracted -- when their focus is divided or elsewhere -- they mis-estimate the passage of time, thinking that less time has passed than actually has -- that time has flown. It's perhaps because of this perception that when Monika Bauerlein and Clara Jeffery described the changes in work-life patterns in a recent issue of Mother Jones, they called them the "great speed-up." The Digital Sabbath isn't the only strategy for dealing with this speed up: The related set of "slow" movements -- slow food, slow travel, even slow science -- have proliferated in recent years.