diff --git a/build.rs b/build.rs
index 2b4098a..26474fb 100644
--- a/build.rs
+++ b/build.rs
@@ -1,71 +1,182 @@
+use lazy_static::lazy_static;
+use regex::Regex;
 use std::env;
+use std::fmt;
 use std::fs::File;
 use std::io::{BufRead, BufReader, BufWriter, Write};
 use std::path::Path;
-use regex::Regex;
-use lazy_static::lazy_static;
 
-lazy_static! {
-    static ref FULL_PATTERN: Regex = Regex::new(r"([A-Z]+)\s\t.+\s\tUTC([−+±]\d{2}(?::\d{2})?)").unwrap();
-    static ref OFFSET_PATTERN: Regex = Regex::new(r"([−+±])(\d{2}(?::\d{2})?)").unwrap();
+/// Error types for build script failures
+#[derive(Debug)]
+enum BuildError {
+    Io(std::io::Error),
+    Regex(String),
+    Parse(String),
+    Env(env::VarError),
 }
 
-const HOUR: u32 = 3600;
+impl fmt::Display for BuildError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            BuildError::Io(e) => write!(f, "IO error: {}", e),
+            BuildError::Regex(msg) => write!(f, "Regex error: {}", msg),
+            BuildError::Parse(msg) => write!(f, "Parse error: {}", msg),
+            BuildError::Env(e) => write!(f, "Environment error: {}", e),
+        }
+    }
+}
 
-fn parse_offset(raw_offset: &str) -> i32 {
-    let capture = OFFSET_PATTERN.captures(raw_offset).expect("RegEx failed to match offset");
-    println!("{}: {}", raw_offset, capture.get(1).expect("First group capture failed").as_str());
+impl From<std::io::Error> for BuildError {
+    fn from(error: std::io::Error) -> Self {
+        BuildError::Io(error)
+    }
+}
 
-    let is_west = capture.get(1).unwrap().as_str() == "−";
-    let time = capture.get(2).expect("Second group capture failed").as_str();
-    let (hours, minutes) = if time.contains(':') {
-        let mut split = time.split(':');
-        let hours = split.next().unwrap().parse::<u32>().unwrap();
-        let minutes = split.next().unwrap().parse::<u32>().unwrap();
+impl From<env::VarError> for BuildError {
+    fn from(error: env::VarError) -> Self {
+        BuildError::Env(error)
+    }
+}
 
-        (hours, minutes)
-    } else {
-        // Minutes not specified, assume 0
-        (time.parse::<u32>().unwrap(), 0)
-    };
+lazy_static! {
+    /// Regex to match timezone lines: "ABBR \t Description \t UTC±HH:MM"
+    static ref TIMEZONE_PATTERN: Regex =
+        Regex::new(r"([A-Z]+)\s\t.+\s\tUTC([−+±]\d{2}(?::\d{2})?)").unwrap();
 
-    let value = (hours * HOUR) + (minutes * 60);
-    return if is_west { value as i32 * -1 } else { value as i32 };
+    /// Regex to parse UTC offset format: "±HH:MM" or "±HH"
+    static ref OFFSET_PATTERN: Regex =
+        Regex::new(r"([−+±])(\d{2})(?::(\d{2}))?").unwrap();
+}
+
+const SECONDS_PER_HOUR: i32 = 3600;
+const SECONDS_PER_MINUTE: i32 = 60;
+
+/// Parse a UTC offset string (e.g., "+05:30", "-08", "±00") into seconds from UTC
+fn parse_utc_offset(raw_offset: &str) -> Result<i32, BuildError> {
+    let captures = OFFSET_PATTERN.captures(raw_offset).ok_or_else(|| {
+        BuildError::Regex(format!("Failed to match offset pattern: {}", raw_offset))
+    })?;
+
+    // Handle ± (variable offset) as UTC
+    let sign = captures.get(1).unwrap().as_str();
+    if sign == "±" {
+        return Ok(0);
+    }
+
+    let hours_str = captures.get(2).unwrap().as_str();
+    let minutes_str = captures.get(3).map(|m| m.as_str()).unwrap_or("0");
+
+    let hours: i32 = hours_str
+        .parse()
+        .map_err(|e| BuildError::Parse(format!("Invalid hours '{}': {}", hours_str, e)))?;
+
+    let minutes: i32 = minutes_str
+        .parse()
+        .map_err(|e| BuildError::Parse(format!("Invalid minutes '{}': {}", minutes_str, e)))?;
+
+    // Validate ranges
+    if hours > 23 {
+        return Err(BuildError::Parse(format!("Hours out of range: {}", hours)));
+    }
+    if minutes > 59 {
+        return Err(BuildError::Parse(format!(
+            "Minutes out of range: {}",
+            minutes
+        )));
+    }
+
+    let total_seconds = (hours * SECONDS_PER_HOUR) + (minutes * SECONDS_PER_MINUTE);
+
+    // Apply sign (− is west/negative, + is east/positive)
+    Ok(match sign {
+        "−" => -total_seconds,
+        "+" => total_seconds,
+        _ => unreachable!("Regex should only match +, −, or ±"),
+    })
+}
+
+/// Parse a single timezone line and extract abbreviation and offset
+fn parse_timezone_line(line: &str) -> Result<Option<(String, i32)>, BuildError> {
+    // Skip comment lines
+    if line.trim().starts_with('#') || line.trim().is_empty() {
+        return Ok(None);
+    }
+
+    let captures = TIMEZONE_PATTERN
+        .captures(line)
+        .ok_or_else(|| BuildError::Regex(format!("Failed to match timezone pattern: {}", line)))?;
+
+    let abbreviation = captures.get(1).unwrap().as_str().to_string();
+    let raw_offset = captures.get(2).unwrap().as_str();
+
+    let offset = parse_utc_offset(raw_offset)?;
+
+    Ok(Some((abbreviation, offset)))
+}
+
+/// Generate the PHF map code for timezone abbreviations to UTC offsets
+fn generate_timezone_map() -> Result<(), BuildError> {
+    let out_dir = env::var("OUT_DIR")?;
+    let output_path = Path::new(&out_dir).join("timezone_map.rs");
+
+    let tz_path = Path::new("./src/abbr_tz");
+    let tz_file = File::open(tz_path)?;
+    let reader = BufReader::new(tz_file);
+
+    let mut out_file = BufWriter::new(File::create(&output_path)?);
+    let mut builder = phf_codegen::Map::<String>::new();
+
+    let mut processed_count = 0;
+    let mut skipped_count = 0;
+
+    for (_line_num, line_result) in reader.lines().enumerate() {
+        let line = line_result?;
+
+        match parse_timezone_line(&line)? {
+            Some((abbreviation, offset)) => {
+                builder.entry(abbreviation.clone(), &offset.to_string());
+                processed_count += 1;
+                println!(
+                    "cargo:warning=Processed timezone: {} -> {} seconds",
+                    abbreviation, offset
+                );
+            }
+            None => {
+                skipped_count += 1;
+            }
+        }
+    }
+
+    // Generate the PHF map
+    writeln!(
+        &mut out_file,
+        "/// Auto-generated timezone abbreviation to UTC offset (in seconds) mapping"
+    )?;
+    writeln!(
+        &mut out_file,
+        "/// Generated from {} timezone definitions ({} processed, {} skipped)",
+        processed_count + skipped_count,
+        processed_count,
+        skipped_count
+    )?;
+    writeln!(
+        &mut out_file,
+        "pub static TIMEZONE_OFFSETS: phf::Map<&'static str, i32> = {};",
+        builder.build()
+    )?;
+
+    println!(
+        "cargo:warning=Generated timezone map with {} entries",
+        processed_count
+    );
+    Ok(())
 }
 
 fn main() {
-    let path = Path::new(&env::var("OUT_DIR").unwrap()).join("codegen.rs");
-    let raw_tz = BufReader::new(File::open("./src/abbr_tz").unwrap());
-
-    let mut file = BufWriter::new(File::create(&path).unwrap());
-
-    let mut builder: phf_codegen::Map<String> = phf_codegen::Map::new();
-
-    for line in raw_tz.lines() {
-        let line = line.unwrap();
-        if line.starts_with('#') {
-            continue;
-        }
-
-        let capture = FULL_PATTERN.captures(&line).expect("RegEx failed to match line");
-
-        let abbreviation = capture.get(1).unwrap().as_str();
-        let raw_offset = capture.get(2).unwrap().as_str();
-
-        let offset = if !raw_offset.starts_with('±') {
-            parse_offset(raw_offset)
-        } else {
-            0
-        };
-
-        builder.entry(String::from(abbreviation), &format!("\"{}\"", offset).to_string());
+    if let Err(e) = generate_timezone_map() {
+        panic!("Build script failed: {}", e);
     }
 
-    write!(
-        &mut file,
-        "static TIMEZONES: phf::Map<&'static str, &'static str> = {}",
-        builder.build()
-    )
-        .unwrap();
-    write!(&mut file, ";\n").unwrap();
-}
\ No newline at end of file
+    // Tell Cargo to re-run this build script if the timezone file changes
+    println!("cargo:rerun-if-changed=src/abbr_tz");
+}
diff --git a/src/abbr.rs b/src/abbr.rs
index df4b597..152c9c9 100644
--- a/src/abbr.rs
+++ b/src/abbr.rs
@@ -1,31 +1,92 @@
 use chrono::FixedOffset;
 
-// Generated by build.rs, phf_codegen
-include!(concat!(env!("OUT_DIR"), "/codegen.rs"));
+// Generated by build.rs - timezone abbreviation to UTC offset mapping
+include!(concat!(env!("OUT_DIR"), "/timezone_map.rs"));
 
-/*
-    Parse an abbreviation of a timezone into a UTC offset.
-    Note: This is not standardized at all and is simply built on a reference of Time Zone abbreviations
-    from Wikipedia (as of 2023-7-20).
- */
+/// Parse a timezone abbreviation into a UTC offset.
+///
+/// This uses a pre-generated map of timezone abbreviations to their UTC offsets
+/// in seconds. The mapping is based on the Wikipedia reference of timezone
+/// abbreviations (as of 2023-07-20).
+///
+/// Note: Timezone abbreviations are not standardized and can be ambiguous.
+/// This implementation uses preferred interpretations for conflicting abbreviations.
+///
+/// # Arguments
+/// * `abbreviation` - The timezone abbreviation (e.g., "CST", "EST", "PST")
+///
+/// # Returns
+/// * `Ok(FixedOffset)` - The UTC offset for the timezone
+/// * `Err(String)` - Error message if abbreviation is not found or invalid
+///
+/// # Examples
+/// ```
+/// use chrono::FixedOffset;
+///
+/// let cst = parse_abbreviation("CST").unwrap();
+/// assert_eq!(cst, FixedOffset::west_opt(6 * 3600).unwrap());
+/// ```
 pub fn parse_abbreviation(abbreviation: &str) -> Result<FixedOffset, String> {
-    let offset_integer_string = TIMEZONES.get(abbreviation);
-    if offset_integer_string.is_none() {
-        return Err("Failed to find abbreviation".to_string());
-    }
+    let offset_seconds = TIMEZONE_OFFSETS
+        .get(abbreviation)
+        .ok_or_else(|| format!("Unknown timezone abbreviation: {}", abbreviation))?;
 
-    let offset = FixedOffset::east_opt(offset_integer_string.unwrap().parse().expect("Failed to parse stored offset"));
-    return offset.ok_or("Failed to parse offset".to_string());
+    // Convert seconds to FixedOffset
+    // Positive offsets are east of UTC, negative are west
+    let offset = if *offset_seconds >= 0 {
+        FixedOffset::east_opt(*offset_seconds)
+    } else {
+        FixedOffset::west_opt(-*offset_seconds)
+    };
+
+    offset.ok_or_else(|| {
+        format!(
+            "Invalid offset for timezone {}: {} seconds",
+            abbreviation, offset_seconds
+        )
+    })
 }
 
-
 #[cfg(test)]
 mod tests {
-    use chrono::FixedOffset;
     use crate::abbr::parse_abbreviation;
+    use chrono::FixedOffset;
 
     #[test]
-    fn parse_offset() {
-        assert_eq!(parse_abbreviation("CST").unwrap(), FixedOffset::west_opt(6 * 3600).unwrap());
+    fn test_parse_cst() {
+        // CST (Central Standard Time) is UTC-6
+        let cst = parse_abbreviation("CST").unwrap();
+        assert_eq!(cst, FixedOffset::west_opt(6 * 3600).unwrap());
     }
-}
\ No newline at end of file
+
+    #[test]
+    fn test_parse_est() {
+        // EST (Eastern Standard Time) is UTC-5
+        let est = parse_abbreviation("EST").unwrap();
+        assert_eq!(est, FixedOffset::west_opt(5 * 3600).unwrap());
+    }
+
+    #[test]
+    fn test_parse_utc() {
+        // UTC should be zero offset
+        let utc = parse_abbreviation("UTC").unwrap();
+        assert_eq!(utc, FixedOffset::east_opt(0).unwrap());
+    }
+
+    #[test]
+    fn test_parse_unknown() {
+        // Unknown abbreviation should return error
+        let result = parse_abbreviation("INVALID");
+        assert!(result.is_err());
+        assert!(result
+            .unwrap_err()
+            .contains("Unknown timezone abbreviation"));
+    }
+
+    #[test]
+    fn test_parse_positive_offset() {
+        // JST (Japan Standard Time) is UTC+9
+        let jst = parse_abbreviation("JST").unwrap();
+        assert_eq!(jst, FixedOffset::east_opt(9 * 3600).unwrap());
+    }
+}