diff --git a/Sources/RemindersLibrary/NaturalLanguage.swift b/Sources/RemindersLibrary/NaturalLanguage.swift
index b9f9baf..41ef53a 100644
--- a/Sources/RemindersLibrary/NaturalLanguage.swift
+++ b/Sources/RemindersLibrary/NaturalLanguage.swift
@@ -1,7 +1,7 @@
 import ArgumentParser
 import Foundation
 
-private let calendar = Calendar.current
+private let calendar = Calendar(identifier: .gregorian)
 private let allComponents: Set<Calendar.Component> = [
     .era, .year, .yearForWeekOfYear, .quarter, .month,
     .weekOfYear, .weekOfMonth, .weekday, .weekdayOrdinal, .day,
diff --git a/Tests/RemindersTests/NaturalLanguageTests.swift b/Tests/RemindersTests/NaturalLanguageTests.swift
index 1ccda53..b7f7fdd 100644
--- a/Tests/RemindersTests/NaturalLanguageTests.swift
+++ b/Tests/RemindersTests/NaturalLanguageTests.swift
@@ -3,10 +3,12 @@ import Foundation
 import XCTest
 
 final class NaturalLanguageTests: XCTestCase {
+    private let calendar = Calendar(identifier: .gregorian)
+
     func testYesterday() throws {
         let components = try XCTUnwrap(DateComponents(argument: "yesterday"))
-        let tomorrow = try XCTUnwrap(Calendar.current.date(byAdding: .day, value: -1, to: Date()))
-        let expectedComponents = Calendar.current.dateComponents(
+        let tomorrow = try XCTUnwrap(calendar.date(byAdding: .day, value: -1, to: Date()))
+        let expectedComponents = calendar.dateComponents(
             calendarComponents(except: timeComponents), from: tomorrow)
 
         XCTAssertEqual(components, expectedComponents)
@@ -14,7 +16,7 @@ final class NaturalLanguageTests: XCTestCase {
 
     func testTodayString() throws {
         let components = try XCTUnwrap(DateComponents(argument: "today"))
-        let expectedComponents = Calendar.current.dateComponents(
+        let expectedComponents = calendar.dateComponents(
             calendarComponents(except: timeComponents), from: Date())
 
         XCTAssertEqual(components, expectedComponents)
@@ -22,43 +24,49 @@ final class NaturalLanguageTests: XCTestCase {
 
     func testTodayNoon() throws {
         let components = try XCTUnwrap(DateComponents(argument: "12:00"))
-        let today = try XCTUnwrap(Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: Date()))
-        let expectedComponents = Calendar.current.dateComponents(calendarComponents(), from: today)
+        let today = try XCTUnwrap(calendar.date(bySettingHour: 12, minute: 0, second: 0, of: Date()))
+        let expectedComponents = calendar.dateComponents(calendarComponents(), from: today)
 
         XCTAssertEqual(components, expectedComponents)
     }
 
     func testTonight() throws {
         let components = try XCTUnwrap(DateComponents(argument: "tonight"))
-        let today = try XCTUnwrap(Calendar.current.date(bySettingHour: 19, minute: 0, second: 0, of: Date()))
-        let expectedComponents = Calendar.current.dateComponents(calendarComponents(), from: today)
+        let today = try XCTUnwrap(calendar.date(bySettingHour: 19, minute: 0, second: 0, of: Date()))
+        let expectedComponents = calendar.dateComponents(calendarComponents(), from: today)
 
         XCTAssertEqual(components, expectedComponents)
     }
 
     func testTomorrow() throws {
         let components = try XCTUnwrap(DateComponents(argument: "tomorrow"))
-        let tomorrow = try XCTUnwrap(Calendar.current.date(byAdding: .day, value: 1, to: Date()))
-        let expectedComponents = Calendar.current.dateComponents(
+        let tomorrow = try XCTUnwrap(calendar.date(byAdding: .day, value: 1, to: Date()))
+        let expectedComponents = calendar.dateComponents(
             calendarComponents(except: timeComponents), from: tomorrow)
 
         XCTAssertEqual(components, expectedComponents)
     }
 
+    func testUsesGregorianCalendar() throws {
+        let components = try XCTUnwrap(DateComponents(argument: "tomorrow"))
+
+        XCTAssertEqual(components.calendar?.identifier, .gregorian)
+    }
+
     func testTomorrowAtTime() throws {
         let components = try XCTUnwrap(DateComponents(argument: "tomorrow 9pm"))
-        let tomorrow = try XCTUnwrap(Calendar.current.date(byAdding: .day, value: 1, to: Date()))
+        let tomorrow = try XCTUnwrap(calendar.date(byAdding: .day, value: 1, to: Date()))
         let tomorrowAt9 = try XCTUnwrap(
-            Calendar.current.date(bySettingHour: 21, minute: 0, second: 0, of: tomorrow))
-        let expectedComponents = Calendar.current.dateComponents(calendarComponents(), from: tomorrowAt9)
+            calendar.date(bySettingHour: 21, minute: 0, second: 0, of: tomorrow))
+        let expectedComponents = calendar.dateComponents(calendarComponents(), from: tomorrowAt9)
 
         XCTAssertEqual(components, expectedComponents)
     }
 
     func testRelativeDayCount() throws {
         let components = try XCTUnwrap(DateComponents(argument: "in 2 days"))
-        let tomorrow = try XCTUnwrap(Calendar.current.date(byAdding: .day, value: 2, to: Date()))
-        let expectedComponents = Calendar.current.dateComponents(
+        let tomorrow = try XCTUnwrap(calendar.date(byAdding: .day, value: 2, to: Date()))
+        let expectedComponents = calendar.dateComponents(
             calendarComponents(except: timeComponents), from: tomorrow)
 
         XCTAssertEqual(components, expectedComponents)
@@ -66,9 +74,9 @@ final class NaturalLanguageTests: XCTestCase {
 
     func testNextSaturday() throws {
         let components = try XCTUnwrap(DateComponents(argument: "next saturday"))
-        let date = try XCTUnwrap(Calendar.current.date(from: components))
+        let date = try XCTUnwrap(calendar.date(from: components))
 
-        XCTAssertTrue(Calendar.current.isDateInWeekend(date))
+        XCTAssertTrue(calendar.isDateInWeekend(date))
     }
 
     // FB8921206
@@ -76,9 +84,9 @@ final class NaturalLanguageTests: XCTestCase {
         // TODO: This should be inverted but DataDetector doesn't support it right now
         XCTAssertNil(DateComponents(argument: "next weekend"))
         // let components = try XCTUnwrap(DateComponents(argument: "next weekend"))
-        // let date = try XCTUnwrap(Calendar.current.date(from: components))
+        // let date = try XCTUnwrap(calendar.date(from: components))
 
-        // XCTAssertTrue(Calendar.current.isDateInWeekend(date))
+        // XCTAssertTrue(calendar.isDateInWeekend(date))
     }
 
     func testSpecificDays() throws {