[mersault@linux ruby]$ irb
2.5.1 :001 > require 'cassandra'
 => true
2.5.1 :002 > Cassandra::Util.encode_timestamp(Time.now)
 => "1634273394"
2.5.1 :003 > Cassandra::Util.encode_time(Time.now)
 => "'2021-10-14 23:49:54 -0500'"
2.5.1 :004 > Cassandra::Util.encode_object(Time.now)
 => "1634273394"
2.5.1 :005 > Cassandra::Util.encode_timestamp(Cassandra::Time.new(1000000000 * 300))
Traceback (most recent call last):
        3: from /home/mersault/.rvm/rubies/ruby-2.5.1/bin/irb:11:in `<main>'
        2: from (irb):5
        1: from /home/mersault/.rvm/gems/ruby-2.5.1@countapp/gems/cassandra-driver-3.2.5/lib/cassandra/util.rb:127:in `encode_timestamp'
NoMethodError (undefined method `to_i' for #<Cassandra::Time:0x00000000031dcf88 @nanoseconds=300000000000>)
Did you mean?  to_s
2.5.1 :006 > Cassandra::Util.encode_time(Cassandra::Time.new(1000000000 * 300))
 => "'00:05:00.000'"
2.5.1 :007 > Cassandra::Util.encode_object(Cassandra::Time.new(1000000000 * 300))
 => "'00:05:00.000'"

CREATE KEYSPACE foo WITH REPLICATION = {'class' : 'SimpleStrategy', 'replication_factor' : 1};
CREATE TABLE foo.bar (key int PRIMARY KEY, ts timestamp);

require 'cassandra'
require 'cassandra/util'
require 'time'

cluster = Cassandra.cluster
session = cluster.connect
stmt = session.prepare "insert into foo.bar (key,ts) values (?,?)"
session.execute stmt, arguments: [1, Time.now]

cqlsh> select * from foo.bar;                                                                                                                                                    

 key | ts
-----+---------------------------------
   1 | 2021-10-15 05:30:53.477000+0000

(1 rows)