While studying conceptual art this quarter I came across the work of Hanne Darboven, a German Conceptual artist (1941-2009) whose work is based on repetition. Her pieces are characteristic of time and capturing that in what she calls the "neutral" language of numbers and symbols. Much of her work takes the structured format of calendars, graph paper and day planners on which she creates works of repetitive symbols and equations that are painstakingly similar. She, as many other conceptual artists' believed that it is in repetition that differences appear. I think this is evident in her work. I was most intrigued by her practice of Daily Writings, which she committed to do without fail, maybe as a way to keep productive, or simply as a means of measuring time.
For more about Conceptual Art, see "Sentences on Conceptual Art" by Sol Lewitt, 1969