Make clear that the constants are strings.
diff --git a/Doc/library/logging.rst b/Doc/library/logging.rst
index 2399f33..dc2555f 100644
--- a/Doc/library/logging.rst
+++ b/Doc/library/logging.rst
@@ -1651,21 +1651,21 @@
You can use the *when* to specify the type of *interval*. The list of possible
values is, note that they are not case sensitive:
- +----------+-----------------------+
- | Value | Type of interval |
- +==========+=======================+
- | S | Seconds |
- +----------+-----------------------+
- | M | Minutes |
- +----------+-----------------------+
- | H | Hours |
- +----------+-----------------------+
- | D | Days |
- +----------+-----------------------+
- | W | Week day (0=Monday) |
- +----------+-----------------------+
- | midnight | Roll over at midnight |
- +----------+-----------------------+
+ +----------------+-----------------------+
+ | Value | Type of interval |
+ +================+=======================+
+ | ``'S'`` | Seconds |
+ +----------------+-----------------------+
+ | ``'M'`` | Minutes |
+ +----------------+-----------------------+
+ | ``'H'`` | Hours |
+ +----------------+-----------------------+
+ | ``'D'`` | Days |
+ +----------------+-----------------------+
+ | ``'W'`` | Week day (0=Monday) |
+ +----------------+-----------------------+
+ | ``'midnight'`` | Roll over at midnight |
+ +----------------+-----------------------+
If *backupCount* is non-zero, the system will save old log files by appending
extensions to the filename. The extensions are date-and-time based, using the