diff --git a/Sources/KanaKanjiConverterModule/Converter/KanaKanjiConverter.swift b/Sources/KanaKanjiConverterModule/Converter/KanaKanjiConverter.swift
index e3d5ad0..10b14d8 100644
--- a/Sources/KanaKanjiConverterModule/Converter/KanaKanjiConverter.swift
+++ b/Sources/KanaKanjiConverterModule/Converter/KanaKanjiConverter.swift
@@ -156,6 +156,7 @@ import EfficientNGram
             result.append(contentsOf: self.unicodeCandidates(inputData))
         }
         result.append(contentsOf: self.toVersionCandidate(inputData, options: options))
+        result.append(contentsOf: self.convertToTimeExpression(inputData))
         return result
     }
 
diff --git a/Sources/KanaKanjiConverterModule/Converter/TimeExpression.swift b/Sources/KanaKanjiConverterModule/Converter/TimeExpression.swift
new file mode 100644
index 0000000..630f7cf
--- /dev/null
+++ b/Sources/KanaKanjiConverterModule/Converter/TimeExpression.swift
@@ -0,0 +1,43 @@
+import Foundation
+
+extension KanaKanjiConverter {
+    func convertToTimeExpression(_ inputData: ComposingText) -> [Candidate] {
+        var candidates: [Candidate] = []
+        let numberString = inputData.convertTarget
+
+        // Check if all chars are digit.
+        if numberString.contains(where: { !($0.isNumber && $0.isASCII) }) {
+            return []
+        }
+        if numberString.count == 3 {
+            let firstDigit = Int(numberString.prefix(1))!
+            let lastTwoDigits = Int(numberString.suffix(2))!
+            if (0...9).contains(firstDigit) && (0...59).contains(lastTwoDigits) {
+                let timeExpression = "\(firstDigit):\(String(format: "%02d", lastTwoDigits))"
+                let candidate = Candidate(
+                    text: timeExpression,
+                    value: -10,
+                    correspondingCount: numberString.count,
+                    lastMid: MIDData.一般.mid,
+                    data: [DicdataElement(word: timeExpression, ruby: numberString, cid: CIDData.固有名詞.cid, mid: MIDData.一般.mid, value: -10)]
+                )
+                candidates.append(candidate)
+            }
+        } else if numberString.count == 4 {
+            let firstTwoDigits = Int(numberString.prefix(2))!
+            let lastTwoDigits = Int(numberString.suffix(2))!
+            if (0...24).contains(firstTwoDigits) && (0...59).contains(lastTwoDigits) {
+                let timeExpression = "\(String(format: "%02d", firstTwoDigits)):\(String(format: "%02d", lastTwoDigits))"
+                let candidate = Candidate(
+                    text: timeExpression,
+                    value: -10,
+                    correspondingCount: numberString.count,
+                    lastMid: MIDData.一般.mid,
+                    data: [DicdataElement(word: timeExpression, ruby: numberString, cid: CIDData.固有名詞.cid, mid: MIDData.一般.mid, value: -10)]
+                )
+                candidates.append(candidate)
+            }
+        }
+        return candidates
+    }
+}
diff --git a/Tests/KanaKanjiConverterModuleTests/ConverterTests/TimeExpressionTests.swift b/Tests/KanaKanjiConverterModuleTests/ConverterTests/TimeExpressionTests.swift
new file mode 100644
index 0000000..34b6a12
--- /dev/null
+++ b/Tests/KanaKanjiConverterModuleTests/ConverterTests/TimeExpressionTests.swift
@@ -0,0 +1,53 @@
+import XCTest
+@testable import KanaKanjiConverterModule
+
+final class TimeExpressionTests: XCTestCase {
+    private func makeDirectInput(direct input: String) -> ComposingText {
+        ComposingText(
+            convertTargetCursorPosition: input.count,
+            input: input.map {.init(character: $0, inputStyle: .direct)},
+            convertTarget: input
+        )
+    }
+
+    func testConvertToTimeExpression() async throws {
+        let converter = await KanaKanjiConverter()
+
+        let input1 = makeDirectInput(direct: "123")
+        let input2 = makeDirectInput(direct: "1234")
+        let input3 = makeDirectInput(direct: "999")
+        let input4 = makeDirectInput(direct: "1260")
+        let input5 = makeDirectInput(direct: "2440")
+        let input6 = makeDirectInput(direct: "")
+        let input7 = makeDirectInput(direct: "あいうえ")
+        let input8 = makeDirectInput(direct: "13122")
+
+        let candidates1 = await converter.convertToTimeExpression(input1)
+        let candidates2 = await converter.convertToTimeExpression(input2)
+        let candidates3 = await converter.convertToTimeExpression(input3)
+        let candidates4 = await converter.convertToTimeExpression(input4)
+        let candidates5 = await converter.convertToTimeExpression(input5)
+        let candidates6 = await converter.convertToTimeExpression(input6)
+        let candidates7 = await converter.convertToTimeExpression(input7)
+        let candidates8 = await converter.convertToTimeExpression(input8)
+
+        XCTAssertEqual(candidates1.count, 1)
+        XCTAssertEqual(candidates1.first?.text, "1:23")
+
+        XCTAssertEqual(candidates2.count, 1)
+        XCTAssertEqual(candidates2.first?.text, "12:34")
+
+        XCTAssertEqual(candidates3.count, 0)
+
+        XCTAssertEqual(candidates4.count, 0)
+
+        XCTAssertEqual(candidates5.count, 1)
+        XCTAssertEqual(candidates5.first?.text, "24:40")
+
+        XCTAssertEqual(candidates6.count, 0)
+
+        XCTAssertEqual(candidates7.count, 0)
+
+        XCTAssertEqual(candidates8.count, 0)
+    }
+}