Terraform: How to convert string to date and timestamp

Overview

When working with Terraform, a popular infrastructure as code (IAC) tool, managing date and timestamp conversions can be crucial for setting up robust and scalable infrastructure setups. Terraform scripts often require handling dates and timestamps when defining resource lifecycles, scheduling tasks, or dealing with external APIs that return or require datetime information.

This tutorial will guide you through converting strings to dates and timestamps in Terraform. With practical examples and step-by-step instructions, we’ll explore how to manipulate datetime strings to enhance your infrastructure automation tasks. Whether you’re a beginner or an intermediate Terraform user looking to refine your skills, the following insights will be valuable.

Understanding the Basics

Before diving into conversions, it’s essential to understand the basic data types and functions Terraform supports for datetime operations. At its core, Terraform provides a primitive string type for handling textual data which includes datetime in ISO 8601 and RFC 3339 formats. To manipulate these string representations into datetime objects, Terraform utilizes the formatdate function.

Simple String to Date Conversion

variable "example_date" {
  description = "A string representation of a date"
  type        = string
  default     = "2023-03-25"
}

output "converted_date" {
  value = formatdate("YYYY-MM-DD", var.example_date)
}

In this example, we defined a simple date string and used the formatdate function to convert it into a format that Terraform can recognize as a date. Although this operation doesn’t change the string’s appearance significantly, it helps Terraform understand that the value is a date, enabling further date-related manipulations.

Converting Date String to Timestamp

variable "time_string" {
  description = "A string representation of a date and time"
  type        = string
  default     = "2023-03-25T15:30:00Z"
}

output "timestamp" {
  value = timeadd("1970-01-01T00:00:00Z", formatdate("YYYY-MM-DD'T'HH:MM:SS'Z'", var.time_string))
}

This snippet shows how to convert a datetime string into a Unix timestamp, which counts the seconds since 00:00, January 1st, 1970 UTC. The timeadd function used here adds the difference between the provided datetime and the Unix epoch to the latter to compute the timestamp.

Advanced Conversion Techniques

Next, we delve into more sophisticated datetime manipulation techniques, such as handling timezone conversions and generating timestamps for specific future or past dates in Terraform scripts.

Timezone Adjustments

locals {
  original_time = "2023-10-05T14:00:00+00:00"
  target_timezone = "America/Los_Angeles"
}

output "timezone_converted" {
  value = timeadd(local.original_time, formatdate("HH:MM", "2023-10-05T07:00:00-07:00"))
}

This example introduces adjusting the timezone of a datetime string. It showcases adding or subtracting hours to align with the target timezone, using the formatdate and timeadd functions in conjunction. Note that this method requires manual calculation of the timezone difference.

Creating Timestamps for Scheduled Tasks

locals {
  start_date = "2024-01-01"
  end_date   = "2024-01-07"
}

output "task_schedule" {
  values = {
    start = formatdate("YYYY-MM-DD'T'HH:MM:SS'Z'", timestamp())
    end   = formatdate("YYYY-MM-DD'T'HH:MM:SS'Z'", timeadd(local.start_date, "7D"))
  }
}

This section demonstrates how to create timestamped schedules for tasks, using the timestamp() function to get the current datetime as a starting point and then calculating an end date by adding a duration to a predefined date. Such techniques are invaluable for workflow automation where tasks need to be executed within specific timeframes.

Conclusion

Through this tutorial, we explored several ways to convert strings into dates and timestamps in Terraform, from basic to advanced scenarios. Understanding how to manipulate and format datetime strings is a crucial skill in infrastructure automation, enabling more precise control over resource deployments, scheduling, and management. As you continue to work with Terraform, incorporating these techniques will help streamline your operations and make your configurations more dynamic and adaptable.