People have kept diaries and recorded notes since writing was invented. But planners as we think of them today have their roots in almanacs. 
Research:

Atkins, Samuel. “Kalendarium Pennsilvaniense.” W. Bradford. 1685. https://books.google.com/books/about/Kalendarium_Pennsilvaniense_Or_America_s.html?id=wT0wAAAAYAAJ
Nichols, Charles L. “Notes on the Almanacs of Massachusetts.” American Antiquarian Society. 1912. https://www.americanantiquarian.org/proceedings/45647891.pdf
Railton, Stephen. “Anti-Slavery Almanacs.” University of Virginia. https://utc.iath.virginia.edu/abolitn/gallaaaf.html
Britannica, The Editors of Encyclopaedia. "almanac". Encyclopedia Britannica, 9 Oct. 2023, https://www.britannica.com/topic/almanac
Badian, E.. "fasti". Encyclopedia Britannica, 22 Dec. 2021, https://www.britannica.com/topic/fasti-Roman-calendar
Winlock, H. E. “The Origin of the Ancient Egyptian Calendar.” Proceedings of the American Philosophical Society, vol. 83, no. 3, 1940, pp. 447–64. JSTOR, http://www.jstor.org/stable/985113
Smith, William, et a. “A Dictionary of Greek and Roman Antiquities.” Albemarle Street, London. John Murray. 1890. Accessed online: https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0063:entry=fasti-cn
Britannica, The Editors of Encyclopaedia. "Richard Pynson". Encyclopedia Britannica, 1 Jan. 2023, https://www.britannica.com/biography/Richard-Pynson
Driver, Martha W. “When Is a Miscellany Not Miscellaneous? Making Sense of the ‘Kalender of Shepherds.’” The Yearbook of English Studies, vol. 33, 2003, pp. 199–214. JSTOR, https://doi.org/10.2307/3509026
Hockey, Thomas et al. (eds.). “The Biographical Encyclopedia of Astronomers.” Springer Reference. New York: Springer, 2007, pp. 1258-1260 https://islamsci.mcgill.ca/RASI/BEA/Zarqali_BEA.htm
“Diaries and Planners Market Size, Share, Growth, and Industry Analysis by Type (Diaries and Planners) By Application (Premium, and Mass), Latest Trends, Regional Insights, and Forecast From 2024 to 2031.” Business Research Insights. April 2023. https://www.businessresearchinsights.com/market-reports/diaries-and-planners-market-102040
Hubrigh, Joachim. “An almanacke, and prognostication, for the yeare of our Lorde God. 1565. : seruing for all Europia, and also most necessary for all students, marchantes, mariners and trauellers, both by sea and lande, composed and gathered by Ioakim Hubrigh, Doctor in Phisick. Also the most principall fayres in Englande, very necessary for people that doe resorte to the same.” Imprinted by Henry Denham for William Pickring. 1565. Accessed online: https://catalog.folger.edu/record/170062?ln=en
Shank, Michael. "Regiomontanus". Encyclopedia Britannica, 2 Jul. 2023, https://www.britannica.com/biography/Regiomontanus
Danforth, Samuel and Royster, Paul (transcriber & editor), "Samuel Danforth's Almanack Poems and Chronological Tables 1647-1649" (1649). Faculty Publications, UNL Libraries. 36. https://digitalcommons.unl.edu/libraryscience/36
“History of The Nautical Almanac.” Astronomical Applications Department, U.S. Government. https://aa.usno.navy.mil/publications/na_history
“William Pierce.” Town Memorials, Winthrop, Massachusetts.” https://winthropmemorials.org/great-allotment/pages/william-pierce.html
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