The day marked the 12th anniversary of the man from Lurgan first joining the club in a £6million move from Leicester City.
As luck would have it, it was also his 100th SPL match as manager of the Hoops.
And Lennon was delighted the party wasn't spoiled by the result, his side surging to a 3-1 victory.
The icing on this particular cake was the fact the win allowed the champions to move three points clear in the defence of their title, with a game in hand.
Coming on the back of their progression to the Champions League last 16, Lennon admits it was a satisfying way to round off one of the most important weeks since he took over the reins in March 2010.
It was fitting Kilmarnock should provide the opposition, given how many times they have figured in major moments of his time at the club.
Not only were they the team Celtic beat when Lennon collected his first medal in the Hoops, from the League Cup in March 2001, they were also the first team he faced when he assumed control initially on an interim basis from Tony Mowbray in what must seem like another lifetime.
The Hoops won that match 3-1 to help Lennon stabilise a badly-listing ship and he reflected: "We won the SPL title at Rugby Park as well the following season.
"We also lost the League Cup final to them this year, so there have been plenty of ups and downs in our games against Kilmarnock.
"I won a couple a titles at Rugby Park as well as a player, so it has been a decent ground for me."
Of course, it is also the ground where they failed to score enough goals to prevent Rangers lifting the title in 2003, just days after Celtic had contested the Uefa Cup final, and ultimately finished the season without a single trophy to show for all their efforts.
But that has been a rare occurrence during Lennon's dozen years connected to the Parkhead club, and he has more good memories than bad.
"It was the anniversary of me signing on Saturday," he smiled. "It feels like only yesterday I was walking in the door.
"We trained at Barrowfield the day before my first game, at Dundee. It was 11 o'clock in the morning – and we had to put the floodlights on.
"Not much has changed, with the weather, at any rate."
Much has changed with regard to the club and the personnel. But one thing remains a reassuring constant – Celtic are competing on all fronts, domestically and in Europe.
And, with their Champions League involvement for the next two months confined to watching the draw for the last 16 a week on Thursday, Lennon anticipates a much more manageable schedule lies ahead.
Hence the reason emerging from this most taxing period of the campaign with daylight between them and the chasing pack in the title race gives so much satisfaction.
The away form has been the catalyst for this, and the manner in which his players took control and dominated in Ayshire was another example of how, when their focus is fully on the job in hand, they are simply uncontainable within the parameters of the Scottish game.
The goals from Scott Brown – with his weaker foot – Joe Ledley and sub Georgios Samaras sent out a warning to the other 11 clubs that the champions are back on the ball.
Cillian Sheridan's well-taken goal in injury-time was more of an irritation to Fraser Forster – booked for kicking the ball away in disgust at losing a clean sheet – than it was any kind of reflection of a threat Killie posed.
Which is why Lennon was so pleased with the anniversary present delivered by his players.
"We looked like a Champions League team on Saturday, and I'm looking for more of that as the season progresses," he said in what must be an ominous warning to the rest of the SPL that the perceived vulnerability of the Hoops is now a thing of the past as their distracted days are behind them.
Lennon continued: "We were fantastic in terms of our application and concentration, and the way we moved the ball around was very, very pleasing.
"Sometimes you can be flat after a game like Wednesday's against Spartak, but they weren't on Saturday.
"It opens up a gap and the rest of the teams have got to catch us. We're looking for a consistency of wins now."
Whether or not Lennon can have consistency of team selection could be a key factor in achieving this goal.
Brown defied the pain, and medical science, to dominate the game at Rugby Park.
His only moment of unease came post-match when the subject of his hip injury, the injections he takes, and the possibility of surgery irked him to the point where he refused to indulge anyone with his thoughts any longer.
Lennon will continue to discuss with his captain and the club's medical team how to proceed with his care, and the possibility of him going under the knife, although reducing, is not completely eliminated.
The major problem this situation brings for Lennon is not knowing from one day until the next whether or not Brown will feel well enough to play.
But, while the injections are allowing him to keep going, his manager can only join the supporters in admiring his pluck and his influence.
Lennon said: "We've started to see Scott come back to his very best. He's the driving force of the team."