Mishandling the Japanese era start date¶
ID: cs/mishandling-japanese-era
Kind: problem
Security severity:
Severity: warning
Precision: medium
Tags:
- reliability
- date-time
Query suites:
- csharp-security-and-quality.qls
Click to see the query in the CodeQL repository
When eras change, calling a date and time instantiation method that relies on the default era can produce an ambiguous date. In the example below, the call to the JapaneseCalendar.ToDateTime method that uses the default era returns different dates depending on whether or not the new era has been defined in the registry.
Recommendation¶
Use specific era when creating DateTime and DateTimeOffset structs from previously stored date in Japanese calendar
Don’t store dates in Japanese format
Don’t use hard-coded era start date for date calculations converting dates from Japanese date format
Use JapaneseCalendar class for date formatting only
Example¶
This example demonstrates the dangers of using current year assumptions in Japanese date conversions
using System;
using System.Globalization;
public class Example
{
public static void Main()
{
var cal = new JapaneseCalendar();
// constructing date using current era
var dat = cal.ToDateTime(2, 1, 2, 0, 0, 0, 0);
Console.WriteLine($"{dat:s}");
// constructing date using current era
dat = new DateTime(2, 1, 2, cal);
Console.WriteLine($"{dat:s}");
}
}
// Output with the Heisei era current:
// 1990-01-02T00:00:00
// 1990-01-02T00:00:00
// Output with the new era current:
// 2020-01-02T00:00:00
// 2020-01-02T00:00:00