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diff --git a/noao/imred/vtel/d1900.x b/noao/imred/vtel/d1900.x
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+++ b/noao/imred/vtel/d1900.x
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+# D1900 -- Function to return the number of days since the turn of the
+# century.
+
+int procedure d1900 (month, day, year)
+
+int	month, day, year		# m,d,y of date
+
+int	mac[12]
+data	mac/0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334/
+
+begin
+	d1900 = 365 * year + (year - 1) / 4 + mac[month] + day
+	if (month >= 3 && mod(year,4) == 0)
+	    d1900 = d1900 + 1
+end