Clarify nanosecond formatting specifier doc

chronotope · Jul 6, 2023 · ac80252 · ac80252
1 parent dfd3cf5
commit ac80252
Showing 1 changed file with 13 additions and 37 deletions.
diff --git a/src/format/strftime.rs b/src/format/strftime.rs
@@ -53,14 +53,14 @@ The following specifiers are available both to formatting and parsing.
 |       |          |                                                                            |
 | `%M`  | `34`     | Minute number (00--59), zero-padded to 2 digits.                           |
 | `%S`  | `60`     | Second number (00--60), zero-padded to 2 digits. [^4]                      |
-| `%f`  | `026490000`   | The fractional seconds (in nanoseconds) since last whole second. [^7] |
-| `%.f` | `.026490`| Similar to `.%f` but left-aligned. These all consume the leading dot. [^7] |
-| `%.3f`| `.026`        | Similar to `.%f` but left-aligned but fixed to a length of 3. [^7]    |
-| `%.6f`| `.026490`     | Similar to `.%f` but left-aligned but fixed to a length of 6. [^7]    |
-| `%.9f`| `.026490000`  | Similar to `.%f` but left-aligned but fixed to a length of 9. [^7]    |
-| `%3f` | `026`         | Similar to `%.3f` but without the leading dot. [^7]                   |
-| `%6f` | `026490`      | Similar to `%.6f` but without the leading dot. [^7]                   |
-| `%9f` | `026490000`   | Similar to `%.9f` but without the leading dot. [^7]                   |
+| `%f`  | `26490000`    | Number of nanoseconds since last whole second. [^7]                   |
+| `%.f` | `.026490`| Decimal fraction of a second. Consumes the leading dot. [^7]               |
+| `%.3f`| `.026`        | Decimal fraction of a second with a fixed length of 3.                |
+| `%.6f`| `.026490`     | Decimal fraction of a second with a fixed length of 6.                |
+| `%.9f`| `.026490000`  | Decimal fraction of a second with a fixed length of 9.                |
+| `%3f` | `026`         | Decimal fraction of a second like `%.3f` but without the leading dot. |
+| `%6f` | `026490`      | Decimal fraction of a second like `%.6f` but without the leading dot. |
+| `%9f` | `026490000`   | Decimal fraction of a second like `%.9f` but without the leading dot. |
 |       |               |                                                                       |
 | `%R`  | `00:34`       | Hour-minute format. Same as `%H:%M`.                                  |
 | `%T`  | `00:34:60`    | Hour-minute-second format. Same as `%H:%M:%S`.                        |
@@ -132,36 +132,12 @@ Notes:
    For the purpose of Chrono, it only accounts for non-leap seconds
    so it slightly differs from ISO C `strftime` behavior.
 
-[^7]: `%f`, `%.f`, `%.3f`, `%.6f`, `%.9f`, `%3f`, `%6f`, `%9f`:
+[^7]: `%f`, `%.f`:
    <br>
-   The default `%f` is right-aligned and always zero-padded to 9 digits
-   for the compatibility with glibc and others,
-   so it always counts the number of nanoseconds since the last whole second.
-   E.g. 7ms after the last second will print `007000000`,
-   and parsing `7000000` will yield the same.
-   <br>
-   <br>
-   The variant `%.f` is left-aligned and print 0, 3, 6 or 9 fractional digits
-   according to the precision.
-   E.g. 70ms after the last second under `%.f` will print `.070` (note: not `.07`),
-   and parsing `.07`, `.070000` etc. will yield the same.
-   Note that they can print or read nothing if the fractional part is zero or
-   the next character is not `.`.
-   <br>
-   <br>
-   The variant `%.3f`, `%.6f` and `%.9f` are left-aligned and print 3, 6 or 9 fractional digits
-   according to the number preceding `f`.
-   E.g. 70ms after the last second under `%.3f` will print `.070` (note: not `.07`),
-   and parsing `.07`, `.070000` etc. will yield the same.
-   Note that they can read nothing if the fractional part is zero or
-   the next character is not `.` however will print with the specified length.
-   <br>
-   <br>
-   The variant `%3f`, `%6f` and `%9f` are left-aligned and print 3, 6 or 9 fractional digits
-   according to the number preceding `f`, but without the leading dot.
-   E.g. 70ms after the last second under `%3f` will print `070` (note: not `07`),
-   and parsing `07`, `070000` etc. will yield the same.
-   Note that they can read nothing if the fractional part is zero.
+   `%f` and `%.f` are notably different formatting specifiers.<br>
+   `%f` counts the number of nanoseconds since the last whole second, while `%.f` is a fraction of a
+   second.<br>
+   Example: 7μs is formatted as `7000` with `%f`, and formatted as `.000007` with `%.f`.
 
 [^8]: `%Z`:
    Since `chrono` is not aware of timezones beyond their offsets, this specifier