diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..61ae8af
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+++ b/Cargo.lock
@@ -0,0 +1,319 @@
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diff --git a/Cargo.toml b/Cargo.toml
index f852ef1..281ee65 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,3 +4,5 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+chrono = "0.4.43"
+chrono-tz = "0.10.4"
diff --git a/src/calendar.rs b/src/calendar.rs
new file mode 100644
index 0000000..9c08fad
--- /dev/null
+++ b/src/calendar.rs
@@ -0,0 +1,176 @@
+use chrono::{TimeDelta, prelude::*};
+use chrono_tz::Tz;
+use std::error::Error;
+use std::fmt;
+
+#[derive(PartialEq, Debug)]
+enum CalendarError {
+    UnknownTimezone(String),
+    WrongTimeFormat,
+    WrongDateFormat,
+    TimezoneConversionFailed(String),
+}
+
+impl fmt::Display for CalendarError {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let message = match *self {
+            Self::UnknownTimezone(ref tz) => format!("Unknown timezone: {}", tz),
+            Self::WrongTimeFormat => "Wrong time format".to_string(),
+            Self::WrongDateFormat => "Wrong date format".to_string(),
+            Self::TimezoneConversionFailed(ref tz) => {
+                format!("Could not convert time to timezone: {}", tz)
+            }
+        };
+
+        f.write_str(&message)
+    }
+}
+
+impl Error for CalendarError {}
+
+fn create_calendar_strings(time: &NaiveTime, padding_hrs: i8) -> Vec<String> {
+    let start = -padding_hrs;
+    let end = padding_hrs;
+    (start..=end)
+        .map(|v| time.overflowing_add_signed(TimeDelta::hours(v.into())).0)
+        .map(|h| h.format("%H:%M").to_string())
+        .collect()
+}
+
+pub fn create_timetable(
+    target_time: &String,
+    target_date: &String,
+    in_timezone: &String,
+    padding_hrs: i8,
+) -> Result<Vec<String>, CalendarError> {
+    let parsed_timezone = in_timezone
+        .parse::<Tz>()
+        .map_err(|_| CalendarError::UnknownTimezone(in_timezone.clone()))?;
+
+    let parsed_time = if let Ok(hour) = target_time.parse::<u32>() {
+        NaiveTime::from_hms_opt(hour, 0, 0).ok_or(CalendarError::WrongTimeFormat)?
+    } else {
+        NaiveTime::parse_from_str(target_time, "%H:%M")
+            .map_err(|_| CalendarError::WrongTimeFormat)?
+    };
+
+    let parsed_date = NaiveDate::parse_from_str(target_date, "%d-%m-%Y")
+        .or_else(|_| NaiveDate::parse_from_str(target_date, "%d-%m"))
+        .map_err(|_| CalendarError::WrongDateFormat)?;
+
+    let datetime = NaiveDateTime::new(parsed_date, parsed_time);
+    let time_in_timezone = parsed_timezone
+        .from_local_datetime(&datetime)
+        .single()
+        .ok_or(CalendarError::TimezoneConversionFailed(in_timezone.clone()))?;
+
+    Ok(create_calendar_strings(
+        &time_in_timezone.time(),
+        padding_hrs,
+    ))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_calendar_string() {
+        assert_eq!(
+            create_calendar_strings(&NaiveTime::from_hms_opt(10, 0, 0).unwrap(), 4),
+            vec![
+                "06:00", "07:00", "08:00", "09:00", "10:00", "11:00", "12:00", "13:00", "14:00"
+            ]
+        );
+    }
+
+    #[test]
+    fn test_calendar_string_overflow() {
+        assert_eq!(
+            create_calendar_strings(&NaiveTime::from_hms_opt(3, 0, 0).unwrap(), 4),
+            vec![
+                "23:00", "00:00", "01:00", "02:00", "03:00", "04:00", "05:00", "06:00", "07:00"
+            ]
+        );
+    }
+
+    #[test]
+    fn test_calendar_string_underflow() {
+        assert_eq!(
+            create_calendar_strings(&NaiveTime::from_hms_opt(22, 0, 0).unwrap(), 4),
+            vec![
+                "18:00", "19:00", "20:00", "21:00", "22:00", "23:00", "00:00", "01:00", "02:00"
+            ]
+        );
+    }
+
+    #[test]
+    fn test_create_timezone() {
+        assert_eq!(
+            create_timetable(
+                &"10".to_string(),
+                &"1-1-2000".to_string(),
+                &"Europe/Prague".to_string(),
+                2
+            )
+            .unwrap(),
+            vec!["08:00", "09:00", "10:00", "11:00", "12:00"]
+        );
+    }
+
+    #[test]
+    fn test_create_timezone_nonzero_minutes() {
+        assert_eq!(
+            create_timetable(
+                &"10:30".to_string(),
+                &"1-1-2000".to_string(),
+                &"Europe/Prague".to_string(),
+                2
+            )
+            .unwrap(),
+            vec!["08:30", "09:30", "10:30", "11:30", "12:30"]
+        );
+    }
+
+    #[test]
+    fn test_create_timezone_wrong_time() {
+        assert_eq!(
+            create_timetable(
+                &"hello".to_string(),
+                &"1-1-2000".to_string(),
+                &"Europe/Prague".to_string(),
+                2,
+            )
+            .unwrap_err(),
+            CalendarError::WrongTimeFormat
+        );
+    }
+
+    #[test]
+    fn test_create_timezone_wrong_date() {
+        assert_eq!(
+            create_timetable(
+                &"10:00".to_string(),
+                &"hello".to_string(),
+                &"Europe/Prague".to_string(),
+                2,
+            )
+            .unwrap_err(),
+            CalendarError::WrongDateFormat
+        );
+    }
+
+    #[test]
+    fn test_create_timezone_wrong_zone_name() {
+        assert_eq!(
+            create_timetable(
+                &"10:00".to_string(),
+                &"1-1-2000".to_string(),
+                &"hello".to_string(),
+                2,
+            )
+            .unwrap_err(),
+            CalendarError::UnknownTimezone("hello".to_string())
+        );
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..1f504fd 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,3 @@
-fn main() {
-    println!("Hello, world!");
-}
+mod calendar;
+
+fn main() {}