This character is a Other Symbol and is commonly used, that is, in no specific script. The character is also known as alchemical symbol for hour.
The glyph is not a composition. Its East Asian Width is wide. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. U+231B offers a line break opportunity at its position, except in some numeric contexts.
The CLDR project calls this character “hourglass done” for use in screen reading software. It assigns these additional labels, e.g. for search in emoji pickers: sand, timer.
This character is designated as an emoji. It will be rendered as colorful emoji on conforming platforms. To reduce it to a monochrome character, you can combine it with Variation Selector-15: ⌛︎ See the Emojipedia for more details on this character’s emoji properties.
U+231A WATCH and U+231B HOURGLASS originated in the “WordPerfect iconic
character set”, from where they were added to Unicode in January, 1991. See
this e-mail for reference.
The Wikipedia has the following information about this codepoint:
An hourglass (or sandglass, sand timer, or sand clock) is a device used to measure the passage of time. It comprises two glass bulbs connected vertically by a narrow neck that allows a regulated flow of a substance (historically sand) from the upper bulb to the lower one due to gravity. Typically, the upper and lower bulbs are symmetric so that the hourglass will measure the same duration regardless of orientation. The specific duration of time a given hourglass measures is determined by factors including the quantity and coarseness of the particulate matter, the bulb size, and the neck width.
Depictions of an hourglass as a symbol of the passage of time are found in art, especially on tombstones or other monuments, from antiquity to the present day. The form of a winged hourglass has been used as a literal depiction of the Latin phrase tempus fugit ("time flies").