The following constants are defined. The entries under Category indicate in which setlocale(3C) category each item is defined.
| Constant | Category | Meaning |
| CODESET | LC_CTYPE | codeset name |
| D_T_FMT | LC_TIME | string for formatting date and time |
| D_FMT | LC_TIME | date format string |
| T_FMT | LC_TIME | time format string |
| T_FMT_AMPM | LC_TIME | a.m. or p.m. time format string |
| AM_STR | LC_TIME | ante-meridiem affix |
| PM_STR | LC_TIME | post-meridiem affix |
| DAY_1 | LC_TIME | name of the first day of the week (for example, Sunday) |
| DAY_2 | LC_TIME | name of the second day of the week (for example, Monday) |
| DAY_3 | LC_TIME | name of the third day of the week (for example, Tuesday) |
| DAY_4 | LC_TIME | name of the fourth day of the week (for example, Wednesday) |
| DAY_5 | LC_TIME | name of the fifth day of the week (for example, Thursday) |
| DAY_6 | LC_TIME | name of the sixth day of the week (for example, Friday) |
| DAY_7 | LC_TIME | name of the seventh day of the week (for example, Saturday) |
| ABDAY_1 | LC_TIME | abbreviated name of the first day of the week |
| ABDAY_2 | LC_TIME | abbreviated name of the second day of the week |
| ABDAY_3 | LC_TIME | abbreviated name of the third day of the week |
| ABDAY_4 | LC_TIME | abbreviated name of the fourth day of the week |
| ABDAY_5 | LC_TIME | abbreviated name of the fifth day of the week |
| ABDAY_6 | LC_TIME | abbreviated name of the seventh day of the week |
| ABDAY_7 | LC_TIME | abbreviated name of the seventh day of the week |
| MON_1 | LC_TIME | name of the first month of the year |
| MON_2 | LC_TIME | name of the second month |
| MON_3 | LC_TIME | name of the third month |
| MON_4 | LC_TIME | name of the fourth month |
| MON_5 | LC_TIME | name of the fifth month |
| MON_6 | LC_TIME | name of the sixth month |
| MON_7 | LC_TIME | name of the seventh month |
| MON_8 | LC_TIME | name of the eighth month |
| MON_9 | LC_TIME | name of the ninth month |
| MON_10 | LC_TIME | name of the tenth month |
| MON_11 | LC_TIME | name of the eleventh month |
| MON_12 | LC_TIME | name of the twelfth month |
| tblbrABMON_1 | LC_TIME | abbreviated name of the first month |
| ABMON_2 | LC_TIME | abbreviated name of the second month |
| ABMON_3 | LC_TIME | abbreviated name of the third month |
| ABMON_4 | LC_TIME | abbreviated name of the fourth month |
| ABMON_5 | LC_TIME | abbreviated name of the fifth month |
| ABMON_6 | LC_TIME | abbreviated name of the sixth month |
| ABMON_7 | LC_TIME | abbreviated name of the seventh month |
| ABMON_8 | LC_TIME | abbreviated name of the eighth month |
| ABMON_9 | LC_TIME | abbreviated name of the ninth month |
| ABMON_10 | LC_TIME | abbreviated name of the tenth month |
| ABMON_11 | LC_TIME | abbreviated name of the eleventh month |
| ABMON_12 | LC_TIME | abbreviated name of the twelfth month |
| ERA | LC_TIME | era description segments |
| ERA_D_FMT | LC_TIME | era date format string |
| ERA_D_T_FMT | LC_TIME | era date and time format string |
| ERA_T_FMT | LC_TIME | era time format string |
| ALT_DIGITS | LC_TIME | alternative symbols for digits |
| RADIXCHAR | LC_NUMERIC | radix character |
| THOUSEP | LC_NUMERIC | separator for thousands |
| YESEXPR | LC_MESSAGES | affirmative response expression |
| NOEXPR | LC_MESSAGES | negative response expression |
| YESSTR | LC_MESSAGES | affirmative response for yes/no queries |
| NOSTR | LC_MESSAGES | negative response ro yes/no queries |
| CRNCYSTR | LC_MONETARY | local currency symbol, preceded by '-' if the symbol sould appear before the
value, '+' if the symbol should appear after the value, or '.' if the symbol should replace the radix character |