diff --git a/Cargo.lock b/Cargo.lock
index b55534b..70c6b0b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -661,6 +661,19 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "chrono"
+version = "0.4.42"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "145052bdd345b87320e369255277e3fb5152762ad123a901ef5c262dd38fe8d2"
+dependencies = [
+ "iana-time-zone",
+ "js-sys",
+ "num-traits",
+ "wasm-bindgen",
+ "windows-link",
+]
+
 [[package]]
 name = "clipboard-win"
 version = "5.4.1"
@@ -1520,6 +1533,30 @@ version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dfa686283ad6dd069f105e5ab091b04c62850d3e4cf5d67debad1933f55023df"
 
+[[package]]
+name = "iana-time-zone"
+version = "0.1.64"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "33e57f83510bb73707521ebaffa789ec8caf86f9657cad665b092b581d40e9fb"
+dependencies = [
+ "android_system_properties",
+ "core-foundation-sys",
+ "iana-time-zone-haiku",
+ "js-sys",
+ "log",
+ "wasm-bindgen",
+ "windows-core 0.58.0",
+]
+
+[[package]]
+name = "iana-time-zone-haiku"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f31827a206f56af32e590ba56d5d2d085f558508192593743f16b2306495269f"
+dependencies = [
+ "cc",
+]
+
 [[package]]
 name = "icu_collections"
 version = "2.1.1"
@@ -2671,6 +2708,7 @@ dependencies = [
 name = "rlogg"
 version = "0.2.0"
 dependencies = [
+ "chrono",
  "eframe",
  "rayon",
  "regex",
diff --git a/Cargo.toml b/Cargo.toml
index 70321bc..5e7cc21 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -17,3 +17,4 @@ regex = "1.11"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 rayon = "1.10"
+chrono = "0.4"
diff --git a/src/config.rs b/src/config.rs
index f6d9342..ab7f034 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -12,6 +12,18 @@ pub struct AppConfig {
     pub last_search_query: String,
     #[serde(default)]
     pub highlight_rules: Vec<HighlightRule>,
+    #[serde(default)]
+    pub date_range_enabled: bool,
+    #[serde(default = "default_date_format")]
+    pub date_format: String,
+    #[serde(default)]
+    pub date_from: String,
+    #[serde(default)]
+    pub date_to: String,
+}
+
+fn default_date_format() -> String {
+    String::from("%Y-%m-%d %H:%M:%S")
 }
 
 impl AppConfig {
diff --git a/src/main.rs b/src/main.rs
index c7e1bbe..2fb6014 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -67,9 +67,10 @@ impl LogViewerApp {
                 case_sensitive: config.case_sensitive,
                 use_regex: config.use_regex,
                 history: config.search_history,
-                date_range_enabled: false,
-                date_from: String::new(),
-                date_to: String::new(),
+                date_range_enabled: config.date_range_enabled,
+                date_format: config.date_format,
+                date_from: config.date_from,
+                date_to: config.date_to,
             },
             indexing_state: IndexingState::new(),
             search_state: SearchState::new(),
@@ -93,6 +94,10 @@ impl LogViewerApp {
             use_regex: self.search_panel_state.use_regex,
             last_search_query: self.search_panel_state.query.clone(),
             highlight_rules: self.highlight_manager.rules.clone(),
+            date_range_enabled: self.search_panel_state.date_range_enabled,
+            date_format: self.search_panel_state.date_format.clone(),
+            date_from: self.search_panel_state.date_from.clone(),
+            date_to: self.search_panel_state.date_to.clone(),
         };
         config.save();
     }
@@ -110,11 +115,40 @@ impl LogViewerApp {
 
     fn handle_search(&mut self) {
         if let Some(tab) = self.active_tab() {
+            // Validate date format if date range is enabled
+            if self.search_panel_state.date_range_enabled {
+                use chrono::NaiveDateTime;
+
+                // Validate format by trying to parse example dates
+                let test_date = "2025-01-01 00:00:00";
+                if NaiveDateTime::parse_from_str(test_date, &self.search_panel_state.date_format).is_err() {
+                    eprintln!("Invalid date format: {}", self.search_panel_state.date_format);
+                    eprintln!("Expected format like: %Y-%m-%d %H:%M:%S");
+                    return;
+                }
+
+                // Validate date_from and date_to can be parsed
+                if !self.search_panel_state.date_from.is_empty() {
+                    if NaiveDateTime::parse_from_str(&self.search_panel_state.date_from, &self.search_panel_state.date_format).is_err() {
+                        eprintln!("Invalid date_from format. Expected format: {}", self.search_panel_state.date_format);
+                        return;
+                    }
+                }
+
+                if !self.search_panel_state.date_to.is_empty() {
+                    if NaiveDateTime::parse_from_str(&self.search_panel_state.date_to, &self.search_panel_state.date_format).is_err() {
+                        eprintln!("Invalid date_to format. Expected format: {}", self.search_panel_state.date_format);
+                        return;
+                    }
+                }
+            }
+
             let params = SearchParams {
                 query: self.search_panel_state.query.clone(),
                 case_sensitive: self.search_panel_state.case_sensitive,
                 use_regex: self.search_panel_state.use_regex,
                 date_range_enabled: self.search_panel_state.date_range_enabled,
+                date_format: self.search_panel_state.date_format.clone(),
                 date_from: self.search_panel_state.date_from.clone(),
                 date_to: self.search_panel_state.date_to.clone(),
             };
diff --git a/src/search.rs b/src/search.rs
index e2e9bef..3ab37ac 100644
--- a/src/search.rs
+++ b/src/search.rs
@@ -5,6 +5,7 @@ use std::io::BufReader;
 use std::path::Path;
 use std::sync::{Arc, Mutex};
 use std::thread;
+use chrono::NaiveDateTime;
 
 use crate::line_index::LineIndex;
 use crate::types::FilteredLine;
@@ -44,6 +45,7 @@ pub struct SearchParams {
     pub case_sensitive: bool,
     pub use_regex: bool,
     pub date_range_enabled: bool,
+    pub date_format: String,
     pub date_from: String,
     pub date_to: String,
 }
@@ -102,6 +104,107 @@ pub fn start_search(
     });
 }
 
+fn format_to_regex(format: &str) -> Option<String> {
+    // Convert chrono format to regex pattern
+    let mut regex = format.to_string();
+    regex = regex.replace("%Y", r"\d{4}");  // 4-digit year
+    regex = regex.replace("%m", r"\d{2}");  // 2-digit month
+    regex = regex.replace("%d", r"\d{2}");  // 2-digit day
+    regex = regex.replace("%H", r"\d{2}");  // 2-digit hour
+    regex = regex.replace("%M", r"\d{2}");  // 2-digit minute
+    regex = regex.replace("%S", r"\d{2}");  // 2-digit second
+    regex = regex.replace("%I", r"\d{2}");  // 2-digit hour (12h)
+    regex = regex.replace("%p", r"(AM|PM)"); // AM/PM
+    Some(regex)
+}
+
+fn extract_and_parse_date(content: &str, format: &str) -> Option<NaiveDateTime> {
+    // Convert format to regex pattern
+    let pattern = format_to_regex(format)?;
+    let regex = Regex::new(&pattern).ok()?;
+    let date_str = regex.captures(content)?.get(0)?.as_str();
+
+    // Parse using the provided format
+    NaiveDateTime::parse_from_str(date_str, format).ok()
+}
+
+fn find_line_with_date(
+    line_index: &LineIndex,
+    file_handle: &mut BufReader<File>,
+    start_line: usize,
+    format: &str,
+    move_down: bool,
+) -> Option<(usize, NaiveDateTime)> {
+    let max_search = 1000; // Search up to 10 lines
+    let range: Box<dyn Iterator<Item = usize>> = if move_down {
+        Box::new(start_line..std::cmp::min(start_line + max_search, line_index.total_lines))
+    } else {
+        Box::new((start_line.saturating_sub(max_search)..=start_line).rev())
+    };
+
+    for line_num in range {
+        if let Some(content) = line_index.read_line(file_handle, line_num) {
+            if let Some(date) = extract_and_parse_date(&content, format) {
+                return Some((line_num, date));
+            }
+        }
+    }
+    None
+}
+
+fn binary_search_date(
+    line_index: &LineIndex,
+    file_handle: &mut BufReader<File>,
+    target_date: &NaiveDateTime,
+    format: &str,
+    find_first: bool, // true = find first occurrence, false = find last
+) -> Option<usize> {
+    let mut left = 0;
+    let mut right = line_index.total_lines;
+    let mut result = None;
+
+    while left < right {
+        let mid = (left + right) / 2;
+
+        // Find a line with a date starting from mid, moving down
+        match find_line_with_date(line_index, file_handle, mid, format, true) {
+            Some((line_with_date, date)) => {
+                if find_first {
+                    // Finding first line >= target_date
+                    if date >= *target_date {
+                        result = Some(line_with_date);
+                        right = mid;
+                    } else {
+                        left = mid + 1;
+                    }
+                } else {
+                    // Finding last line <= target_date
+                    if date <= *target_date {
+                        result = Some(line_with_date);
+                        // Ensure we make progress in the binary search
+                        left = mid + 1;
+                    } else {
+                        right = mid;
+                    }
+                }
+            }
+            None => {
+                // Can't find a date near mid, try searching in a larger range
+                // or skip this section
+                if find_first {
+                    // When finding first, if we can't find a date, try the right half
+                    left = mid + 1;
+                } else {
+                    // When finding last, if we can't find a date, try the left half
+                    right = mid;
+                }
+            }
+        }
+    }
+
+    result
+}
+
 fn find_date_range(
     params: &SearchParams,
     line_index: &LineIndex,
@@ -111,35 +214,23 @@ fn find_date_range(
         return None;
     }
 
+    // Parse the target dates using the provided format
+    let date_from = NaiveDateTime::parse_from_str(&params.date_from, &params.date_format).ok()?;
+    let date_to = NaiveDateTime::parse_from_str(&params.date_to, &params.date_format).ok()?;
+
     let file = File::open(file_path).ok()?;
     let mut file_handle = BufReader::new(file);
 
-    let mut start_line = None;
-    let mut end_line = None;
+    // Binary search for first line >= date_from
+    let start_line = binary_search_date(line_index, &mut file_handle, &date_from, &params.date_format, true)?;
 
-    // Find first line containing date_from text
-    for line_num in 0..line_index.total_lines {
-        if let Some(content) = line_index.read_line(&mut file_handle, line_num) {
-            if content.contains(&params.date_from) {
-                start_line = Some(line_num);
-                break;
-            }
-        }
-    }
+    // Binary search for last line <= date_to
+    let end_line = binary_search_date(line_index, &mut file_handle, &date_to, &params.date_format, false)?;
 
-    // Find last line containing date_to text
-    for line_num in (0..line_index.total_lines).rev() {
-        if let Some(content) = line_index.read_line(&mut file_handle, line_num) {
-            if content.contains(&params.date_to) {
-                end_line = Some(line_num + 1); // +1 to include this line
-                break;
-            }
-        }
-    }
-
-    match (start_line, end_line) {
-        (Some(start), Some(end)) if start < end => Some((start, end)),
-        _ => None,
+    if start_line < end_line {
+        Some((start_line, end_line + 1)) // +1 to include the end line
+    } else {
+        None
     }
 }
 
diff --git a/src/ui/search_panel.rs b/src/ui/search_panel.rs
index 42575d0..3054173 100644
--- a/src/ui/search_panel.rs
+++ b/src/ui/search_panel.rs
@@ -9,6 +9,7 @@ pub struct SearchPanelState {
     pub use_regex: bool,
     pub history: Vec<String>,
     pub date_range_enabled: bool,
+    pub date_format: String,
     pub date_from: String,
     pub date_to: String,
 }
@@ -110,6 +111,16 @@ pub fn render_search_panel(
                 // Date range fields (show when date_range_enabled is true)
                 if state.date_range_enabled {
                     ui.add_space(6.0);
+                    ui.horizontal(|ui| {
+                        ui.label("Format:");
+                        ui.add(
+                            egui::TextEdit::singleline(&mut state.date_format)
+                                .desired_width(200.0)
+                                .hint_text("%Y-%m-%d %H:%M:%S")
+                        );
+                    });
+
+                    ui.add_space(4.0);
                     ui.horizontal(|ui| {
                         ui.label("From:");
                         ui.add(