C# DateTime.ToString Format Strings

C# DateTime.ToString Format Strings

C# provides both standard (single-character) and custom (multi-character) format specifiers for DateTime.ToString(). The custom format strings use a token system similar to Java's DateTimeFormatter.

Custom Format Specifiers

Specifier	Meaning	Example
yyyy	Year (4-digit)	2026
yy	Year (2-digit)	26
MMMM	Full month name	February
MMM	Abbreviated month	Feb
MM	Month (zero-padded)	02
M	Month (no padding)	2
dddd	Full weekday	Saturday
ddd	Abbreviated weekday	Sat
dd	Day (zero-padded)	28
d	Day (no padding)	28
HH	Hour 24h (zero-padded)	14
H	Hour 24h (no padding)	14
hh	Hour 12h (zero-padded)	02
h	Hour 12h (no padding)	2
mm	Minute (zero-padded)	30
m	Minute (no padding)	30
ss	Second (zero-padded)	00
fff	Milliseconds	123
tt	AM/PM	PM
zzz	Offset (+HH:mm)	+09:00
K	Timezone info	+09:00 or Z

Standard Format Specifiers

Single-character shortcuts that expand to culture-aware patterns:

Specifier	Name	en-US Example
d	Short date	2/28/2026
D	Long date	Saturday, February 28, 2026
t	Short time	2:30 PM
T	Long time	2:30:00 PM
f	Full (short time)	Saturday, February 28, 2026 2:30 PM
F	Full (long time)	Saturday, February 28, 2026 2:30:00 PM
g	General (short time)	2/28/2026 2:30 PM
G	General (long time)	2/28/2026 2:30:00 PM
o	Round-trip	2026-02-28T14:30:00.0000000+09:00
s	Sortable	2026-02-28T14:30:00
u	Universal sortable	2026-02-28 14:30:00Z
r/R	RFC 1123	Sat, 28 Feb 2026 14:30:00 GMT

Usage Examples

DateTime dt = new DateTime(2026, 2, 28, 14, 30, 0);

dt.ToString("yyyy-MM-dd");           // "2026-02-28"
dt.ToString("yyyy-MM-dd HH:mm:ss");  // "2026-02-28 14:30:00"
dt.ToString("MMMM d, yyyy");         // "February 28, 2026"
dt.ToString("ddd, dd MMM yyyy");     // "Sat, 28 Feb 2026"
dt.ToString("hh:mm tt");             // "02:30 PM"
dt.ToString("o");                    // Round-trip format

// Culture-specific
dt.ToString("d", new CultureInfo("de-DE")); // "28.02.2026"
dt.ToString("d", new CultureInfo("ja-JP")); // "2026/02/28"

Escaping Literal Characters

Use single quotes or backslash to include literal characters:

dt.ToString("'Date:' yyyy-MM-dd");  // "Date: 2026-02-28"
dt.ToString("yyyy\-MM\-dd");       // "2026-02-28"

DateTimeOffset

For timezone-aware dates, use DateTimeOffset:

DateTimeOffset dto = new DateTimeOffset(2026, 2, 28, 14, 30, 0,
    TimeSpan.FromHours(9));
dto.ToString("yyyy-MM-ddTHH:mm:sszzz"); // "2026-02-28T14:30:00+09:00"
dto.ToString("o"); // Full precision round-trip