Unix Timestamps in Ruby and Rails

Ruby's Time class handles Unix timestamps natively. Rails adds ActiveSupport::TimeWithZone for robust timezone handling. Here are the essential patterns.

Get the current Unix timestamp

Time.now.to_i returns the current epoch in seconds. Use Time.now.to_f for float precision.

# Seconds since epoch (integer)
Time.now.to_i         # => 1700000000

# Seconds with fractional precision
Time.now.to_f         # => 1700000000.123456

# Rails: UTC-aware current time
Time.current.to_i     # => 1700000000

Convert a Unix timestamp to a Time object

Time.at() converts epoch seconds to a Time object. Chain .utc to ensure UTC output.

# From seconds
t = Time.at(1700000000)
puts t.utc           # => 2023-11-14 22:13:20 UTC
puts t.iso8601       # => "2023-11-14T22:13:20+00:00"

# From milliseconds
t = Time.at(1700000000000 / 1000.0)
puts t.utc.iso8601

Rails: timezone-aware timestamps

In Rails, always use Time.current instead of Time.now to respect the app's configured timezone.

# Convert epoch to Rails TimeWithZone
ts = 1700000000
time = Time.zone.at(ts)
puts time            # => Tue, 14 Nov 2023 22:13:20 UTC +00:00

# ActiveRecord: created_at returns TimeWithZone automatically
user = User.find(1)
puts user.created_at.to_i   # epoch seconds
puts user.created_at.iso8601