Cookbooks
Lua
Chapter 7. Dates and Times
Parsing a date from a string

Lua:
Parsing a date from a string

How to:

Lua does not have built-in support for date and time manipulation beyond the limited functionality provided by the os.date and os.time functions. However, these can be leveraged for basic parsing, and for more complex requirements, the luadate library, an external library, can be utilized.

Using os.date and os.time:

-- Convert a human-readable date to a timestamp and back
local dateString = "2023-09-21 15:00:00"
local pattern = "(%d+)-(%d+)-(%d+) (%d+):(%d+):(%d+)"
local year, month, day, hour, minute, second = dateString:match(pattern)

local timestamp = os.time({
  year = year,
  month = month,
  day = day,
  hour = hour,
  min = minute,
  sec = second
})

-- Convert timestamp back to a human-readable format
local formattedDate = os.date("%Y-%m-%d %H:%M:%S", timestamp)
print(formattedDate)  -- Output: 2023-09-21 15:00:00

Using luadate (third-party library): To use luadate, ensure it is installed via LuaRocks or your package manager of choice. luadate adds extensive date and time parsing and manipulation capabilities.

local date = require('date')

-- Parse a date string directly
local parsedDate = date.parse("2023-09-21 15:00:00")
print(parsedDate:fmt("%Y-%m-%d %H:%M:%S"))  -- Output: 2023-09-21 15:00:00

-- Adding durations
local oneWeekLater = parsedDate:adddays(7)
print(oneWeekLater:fmt("%Y-%m-%d %H:%M:%S"))  -- Output: 2023-09-28 15:00:00

The luadate library offers a more intuitive and powerful way to work with dates, including parsing from strings, formatting, and arithmetic operations on dates, which considerably simplifies working with temporal data in Lua.

Getting the current date