UPDATE: Dump of initial files

base/src/formatter/dates.rs

@@ -0,0 +1,17 @@
+use chrono::Datelike;
+use chrono::Duration;
+use chrono::NaiveDate;
+
+use crate::constants::EXCEL_DATE_BASE;
+
+pub fn from_excel_date(days: i64) -> NaiveDate {
+    let dt = NaiveDate::from_ymd_opt(1900, 1, 1).expect("problem with chrono::NaiveDate");
+    dt + Duration::days(days - 2)
+}
+
+pub fn date_to_serial_number(day: u32, month: u32, year: i32) -> Result<i32, String> {
+    match NaiveDate::from_ymd_opt(year, month, day) {
+        Some(native_date) => Ok(native_date.num_days_from_ce() - EXCEL_DATE_BASE),
+        None => Err("Out of range parameters for date".to_string()),
+    }
+}