I tried to go through the Manga...
East Blue Saga : about 15 days, Grand Line : About 77 days, New World
: about 41 days
Total : 2 years 134 days or about 2 years and 4 months
** - (didn't seem to have food to travel for more than a day)
Day 1 : Luffy leaves Fuusha Village
Day 2** : Luffy is sucked into a whirlpool and ends up in Alvida's
Day 3** : Luffy and Coby free Zoro
Day 4** : Luffy and Zoro reach Orange town, meet Gaimon
Day 5** : Luffy arrives at Syrup Village
Day 6 : Luffy defeats Kuro
Day 7 : Usopp joins, Strawhats get Merry, Usopp paints the Strawhat
Jolly Roger, Strawhats meet Johnny and Yosaku
Day 10 : (Johnny says it takes 2-3 days to reach Baratie) Strawhats
Day 11 : (it says 2 days later) Don Krieg attacks Baratie and is
defeated, sanji joins, Nami arrives at Arlong Park, Zoro is captured,
Nami frees Zoro, Luffy arrives at Arlong park, Luffy defeats Arlong,
party through the night
Day 13 : Cocoyashi village still parties
Day 14 : Luffy leaves Cocoyashi village
Day 15 : Luffy finds out his bounty, Luffy arrives in Loguetown, is
almost executed, leaves loguetown
Since entering Grand Line..
Day 1 : Arrive at Twin Capes, get Log Pose, head to Whiskey Peak,
reach Whiskey peak at sun down, spend the night at whiskey peak.
Day 2 : Leave Whiskey peak in the morning, arrive at little garden,
leave little garden.
Day 5 : (Kureha tells Nami that she had been infected for 3 days)
Arrive at Drum kingdom, leave Drum kingdom at night.
Day 10 : (stated that 5 days have passed since leaving Drum kingdom)
Meet Bon Clay on their way to Alabasta.
Day 14 (atleast) : (Luffy says its been 4 days since he last ate)
Arrive at Alabasta, meet Ace, reach Yuba at night
Day 15 : Leave Yuba in the morning, change plans and head to rainbase.
Day 16 : (Vivi said Rainbase was a day's walk from Yuba) Reach
Rainbase, head for Alubarna, Luffy beats crocodile.
Day 19 : (Vivi says Luffy was sleeping for 3 days) Luffy wakes up,
Strawhats leave Alubarna at night to find Merry.
Day 20 : Bid farewell to Vivi and leave Alabasta, find Robin on their
ship, a ship falls from the sky, Strawhats head for Jaya, Luffy beats
Day 21 : Strawhats ride the Knock-up Stream to Skypiea, spend the
night planning on finding golden city.
Day 22 : Luffy defeats Enel, party at night
Day 23 : Strawhats leave skypiea
Day 24 (maybe) : Strawhats arrive at Long ring Long Land, win the Davy
Back fight, lose to Aokiji.
Day 28 : (It says that Luffy and Robin needed to rest for 4 days after
being frozen) Strawhats arrive at Water 7, Usopp fights Luffy, Robin
tries to assassinate Iceburg at night
Day 29 : Strawhats try to meet Robin at night, face CP9, lose, set out
for Enies Lobby
Day 30 : CP9 is defeated, Strawhats bid farewell to Merry.
Day 32 : (It says 2 days since the incident) Franky promises to build
Sunny, Luffy meets Garp
Day 35 : (It says 3 days after waiting for Sunny) Strawhats leave
Water 7 on board Sunny.
Day 36 (probably) : Strawhats enter thriller bark, beat moria before
Day 37 : Zoro takes Luffy's pain, Brook joins the crew
Day 39 : (It says 2 days later) Zoro wakes up, Strawhats leave
Day 44 (may be) : (It says several days later) Strawhats reach the Red
Line, rescue Hacchi, head to Saboady, get sent away by Kuma.
Day 47 : (Sentoumaru says people sent by Kuma fly for 3 days) Luffy
arrives at Amazon Lily, fights Boa sisters, parties at night, finds
out about Ace's execution, leaves Amazon Lily at night.
Day 53 : (Gloriosa said Ace was about to be executed in 6 days)
Paramount war, Ace dies, Luffy escapes on Law's submarine
Day 67 : (It says 2 weeks since Paramount war) Luffy wakes up, meets
Rayleigh, decides to take a 2 year time skip
Day 72 (may be) : (assuming it takes 5 days to reach marineford from
amazon lily) Luffy sends the message 3D2Y to the crew
Day 77 (maybe) : (5 days return journey) Luffy starts training on
2 years later...
Day 1 : Arrive at Saboady, reach fishman island, defeat Hody, party
through the night.
Day 2 : Leave fishman island, arrive at Punk Hazard, defeat Caesar,
leave Punk Hazard
Day 3 : Doffy's resignation announced, crew arrives at dressrosa,
defeats Doffy, half the crew head to zou.
Day 13 : (they say Jack left 10 days ago because of Doffy's defeat)
rest of the crew arrives at Zou, parties though the night
Day 14 : Kinemon reaches the top of the elephant, Robin deciphers the
road poneglyph, Jack attacks Zou, Zunesha defeats Jack, half the crew
leaves for Tottoland
Day 21 : (assuming it took 1 week to reach Tottoland) Luffy arrives at
Day 22 : Luffy arrives at Whole Cake island, fights Cracker through
Day 23 : Sanji beats Luffy, Luffy fights the enraged Army, is
captured, escapes, eats Sanji's food
Day 24 : Luffy meets Bege, Tea party is ruined, Luffy fights Katakuri,
the crew escapes Tottoland at night
Day 25 : Luffy is announced the fifth emperor, Revolutionaries save
Day 27 : (2 days after Lulusia kingdom is saved) Reverie begins
Day 31 : (we get the news of the 4th day of reverie) Moria invades
Blackbeard's island, Act 2 begins, Luffy beats Dobon
Day 32 : Komurasaki dies
Day 33 : Komurasaki's wake is cancelled
Day 34 : Komurasaki's funeral, Yasuie dies, Big mom arrives in Udon,
Udon is conquered by Luffy, Big mom and Kaido clash
Day 36 : Big mom and Kaido form an Alliance
Day 41 : (one week since Reverie ends) Raid on Onigashima begins on
the day of the Fire festival