| 1887 | Reopening of Sandakan mission by Fr Byron |
| 1979 | Preached Redemptorist mission in Labuan |
May 1
| 1965 | Foundation of St Martin Secondary School Tempasak Tambunan by Fr Michael Henselmans mhm |
| 1980 | Priestly ordination of Deacon Primus Jouil St Michael Penampang by Bp Fung |
| 1982 | Fundraising walkaton organised by Sabah Catholic Welfare Association |
| 1988 | Inaugural ecumenical conference (RC, Anglican, Basel, PCS, SIB, Baptist) Kundasang |
| 2003 | “Confluence of Spiritual Energies” Symposium organised by Jesuit Companions in Indigenous Ministry (JCIM) East Asia & Oceania and Pacos Trust Sabah, Tambunan |
| 2012 | Kudat hosts 15th KK Archdiocesan Kaamatan Festival |
| 2013 | Perpetual profession of Friar Gilbert James ofmcap SHC |
| 2018 | Pre-PAX Gathering SHPC |
May 2
| 2004 | 10th KK Diocesan Kaamatan Celebration SHC May 2-3 |
| 2016 | KK Archdiocesan Kaamatan Celebration Telipok |
May 3
| 1987 | Blessing of St Mary Parish Centre Sandakan by Bishop-Elect Lee |
| 1989 | 3rd unit (present diocesan bookshop) in Taman Hiburan bought by KK Diocese |
| 1999 | 5th Keningau Diocesan Day hosted by St Anthony Tenom |
| Bible seminar by Fr Lucien Legrand May 3-16 (clergy May 3-7; religious May 8-9; KK May 10-11; Sandakan May 13-14; Tawau May 15-16). | |
| 2003 | Seminar on Children’s Liturgy of the Word in Inanam |
| 2016 | Priestly ordination of Deacon Joshua Liew Chi Khiong by Abp Wong, SHC KK |
May 4
| 1897 | Appointment of Fr Edmund Dunn as 3rd Apostolic Prefect |
| 1996 | Launching of DOPP theme song Seruan Pembaharuan at St John Tuaran |
| 2001 | Inaugural educators conference KK May 4-6 |
| 2003 | Fr Gilbert Engan appointed Keningau vicar general |
| 2014 | Death of Fr Peter van Gestel mhm |
| 2015 | Priestly ordination of Deacon Abel Madisang by Abp Wong, Ranau |
May 5
| 1985 | Priestly ordination of Deacon Calistus Emmanuel CSsR by Bp Fung, Limbahau |
| 1990 | Launching of FSP cassette album Mororobuat composed/sung by Msgr Piong, Dewan Penampang Central Parish Centre. |
| 1996 | Priestly ordination of Deacon Daniel Lim ocd by Bp Lee, St Simon Likas |
| 2003 | Regional Annual Young Priests Gathering BTRC May 5-9 |
| 2012 | Holy Spirit Sook becomes a parish |
| Sook hosts 19th Keningau Diocesan Day | |
| Launching of “A Glimpse of A Mystery” by Fr Charles Chiew, Holy Spirit Sook. Research on the deaths of Msgr August Wachter and companions in Tenom in 1945. |
May 6
| 1973 | Formation of CWL Labuan |
| 1992 | Visit of Fr William vd Salm after four years May 6-25 |
| 1993 | Episcopal ordination/installation of Msgr Cornelius Piong as bishop of Keningau |
| 2001 | 19th Sabah students camp Limbahau |
| 2010 | Death of Fr Augustine Amandus |
| 2018 | 25th anniversary of Keningau Diocese / Episcopal ordination of Bp Cornelius Piong (celebration on May 4-5) |
May 7
| 1944 | Death of Fr John Staal mhm |
| 1979 | Fr Jan van Velzen leaves Sabah for good |
| 1999 | PRW in Tanjung Aru and Penampang May 7-9 |
| 2003 | Death of Fr Frank Cowan, Freshfield England |
May 8
| 1894 | Blessing of Inobong Church |
| 1987 | 7th PAX Youth Assembly CDC May 8-11 |
| 1989 | Peter Thien & Derek Chong attend evangelization course in Malta |
| 1999 | Bible study seminar CDC |
| 2016 | 50th WCD celebration: Communication & Mercy: A Fruitful Encounter, Kundasang |
May 9
| 1995 | Bible exhibition held in conjunction with Bible Sunday Tawau |
| 1998 | 66 participants from KK & Keningau attend inaugural national catechists conference Majodi Centre Plentong |
| 2003 | Death of Fr Herman Saraber mhm in Holland |
| 2018 | 14th General Election (GE14): Pakatan Harapan (Hope Alliance) under Tun Dr Mahathir Mohamad toppled UMNO after 60 years |
May 10
| 1992 | 70th foundation anniversary of SM Holy Trinity Tawau |
| 1994 | Teachers Day celebration for St Francis/Shan Tao Kindergartens |
| 1995 | Recollection for Sunday School teachers, Benildus Hse Tg Aru |
| 2002 | Journalism seminar organised by DSCC Tg Aru |
May 11
| 1946 | Priestly ordination of Deacon John Baptist Yong by Bp Voltoter in Hong Kong |
| 1981 | Seminar on social justice, evangelization & presbyterate for clergy by Jesuit Frs Catalino Arevalo & Antonio Lambino KK Seminary May 11-15 |
| 1990 | Labuan youth seminar May 11-13 |
| 1996 | Launching of DOPP theme song CDC |
| 1998 | 5th KK Diocesan Kaamatan celebration hosted by Kiulu |
May 12
| 1991 | 5th Good Tidings Festival Sandakan |
| 1996 | Football match between seminarians & KSFX youths KSFX |
May 13
| 1987 | Silver jubilee of Sr Rosemary (Elizabeth) Lee of the Blessed Sacrament ocd |
| 1994 | Blessing of new De La Salle Centre & Archives by Bp Lee May 13-14 |
May 14
| 1988 | Parents catechetical seminar SHPC |
| 1989 | 3rd Good Tidings Festival Sandakan |
| 1995 | Pastoral visit of Bp Lee & PAX officials to Sandakan |
| 1999 | PRW in Bundu Tuhan/Ranau/Telupid May 14-16 |
May 15
| 1891 | Fr Rientjer drowns in Putatan River |
| 1949 | Death of Rt Rev Aloysius Hopfgartner mhm |
| 1977 | Formation of Tawau Timorese community under Apolinaris Mado |
| 1982 | Formation of 4th KK Company of Boys Brigade SHPH |
| Youth leadership seminar in Limbanak | |
| 1988 | 17th PAX Assembly BTRC May 15-17 |
| 1990 | Secondary school students awareness camp BTRC May 15-20 |
| 1991 | 2nd Sabah CCR conference May 15-19 |
| 2003 | 9th KK Diocesan Kaamatan celebration Sandakan |
| 2015 | Final profession of Robin Lomangkok CSsR Church of Risen Christ Singapore |
May 16
| 1889 | Fr Goossens return from England with four Franciscan Missionaries of St Joseph – Srs Clare, Bonaventura, Stanislaus & Baptista. Fr Prenger leaves for London. |
| 1948 | Death of Fr Henry Janssen mhm |
| 1976 | Bishop Fung visits Keningau |
| 1983 | Liturgical seminar in Sandakan by Fr Makajil and Fr Tung |
| 1996 | Launching of DOPP theme song in Lahad Datu |
May 17
| 1981 | Talk for teachers by La Salle Br Patrick Lo Tg Aru |
| 1986 | Silver jubilee of Sr Aquinas (Rosemary Rosalind) Voon fsic |
| 1987 | Inaugural Nurses Day Mass in Tawau |
| 2000 | Death of Fr Willibrord Smit mhm |
| 2003 | Priestly ordination of Deacon Valentine Gampok ofmcap by Bp Piong, Tambunan |
May 18
| 1969 | Formation of Tuaran parish council |
| 1974 | Bishop Chung visits Kudat May 18-20 |
| 1982 | Redemptorist preached mission in SHC KK |
| 2000 | Death of Anthonius Balunting, father of Fr Bede |
| 2003 | Inaugural combined Kaamatan/Gawai Mass for East Malaysians in Kuantan |
May 19
| 1945 | Japanese invaders round up Msgr Wachter, Frs Unterberger, Bhom, Theurl & Obertegger, Br Aegidus & laymen Patrick Lee, Stanislaus Sabahai & Peter Wong in Penampang; Frs Raich, Flur & Paulmichi in Kinuta and take them to Sapong Tenom where they died between July 1 and Aug 15. |
| 1977 | Installation of Bp Fung as Bishop of KK Diocese. |
| 1995 | 31st National AGM of Boys Brigade May 19-20 |
| 2000 | Seminar on Catechism of the Catholic Church (CCC) by Helene Reichl BTRC May 19-21 |
May 20
| 1995 | Bible training course BTRC May 20-26 |
| 1996 | Limbahau hosts 3rd KK Diocesan Kaamatan celebration |
May 21
| 2017 | Archdiocesan celebration of CCR golden jubilee SHC |
May 22
| 1983 | Teachers recollection SM La Salle Tg Aru |
| 1988 | 2nd Good Tidings Festival Sandakan |
| 1994 | 8th Good Tidings Festival Sandakan |
May 23
| 1989 | RCIA seminar by Fr Oswald Hirmer May 23-26 SHC |
| 1999 | 13th Good Tidings Festival Sandakan |
| 2001 | Fr Gerard Preyde leaves Sabah for good |
| 2002 | Chinese CCC seminar by Helene Reichl BTRC May 23-26 |
| 2008 | KK Diocese elevated to Archdiocese by Benedict XVI with Bp Lee as metropolitan archbishop |
| 2018 | 10th anniversary of KK Archdiocese |
May 24
| 1984 | Frs William Poilis & Joseph Liansim and Shirley Kandilis leave for a 3-week ecumenical tour of West Germany/mission festival organised by the Evangelical Church of Wurtemberg Heilbronn |
| 1993 | Sandakan teachers day celebration |
| 2002 | Keningau diocesan youth leadership programme May 24-26 |
May 25
| 1963 | Consecration of Stella Maris Church Tg Aru by Bishop Buis |
| 1994 | Penampang hosts Inaugural KK diocesan kaamatan celebration |
| 9th Sandakan annual delegates assembly | |
| 1996 | Death of Fr Jan Goedhart mhm |
| 2001 | Inaugural youth leadership formation programme BTRC May 25-27 |
| 2015 | Memorandum signed between Abp Wong and Marist Brothers to work in the campus ministry at St Simon Educational Complex Likas |
May 26
| 1991 | “Life process in transition” seminar for FSICs Tg Aru May 26-31 |
| 1996 | Death of Fr Jan Goedhart mhm, 56, of cancer in Tilburg Holland |
May 27
| 2001 | Priestly ordination of Deacon Anthony Mikat by Bp Piong KSFX Keningau |
| 2017 | Silver jubilee celebration of Fr Aloysius Fidelis Holy Rosary Limbahau |
| 2018 | 10th anniversary of Sandakan Diocese Catholic Women’s Apostolate |
May 28
| 1971 | New minor seminary of the Immaculate Conception opened by Fr Mullen, representative of the Apostolic Delegate, blessed by Bishop Buis |
| 1988 | 7th PAX Raffle Draw |
| 1992 | Student leaders fellowship-seminary KK Seminary May 28-30 |
| 1993 | Retreat & induction of members of Association of Pauline Cooperators by Fr Dominador Guzman ssp, Kipovo Penampang May 28-29 |
| 1999 | KK youth rally SM Shan Tao Likas |
May 29
| 1882 | Arrival of Frs A Keyzer & B Pundleider |
| 2002 | CCC seminar by Helene Reichl in Tg Aru May 29-June 1 |
| 2018 | Ranau hosts Archdiocesan Kaamatan Celebration May 28-29 |
May 30
| 1992 | Malaysia-Brunei Legion of Mary gathering BTRC May 30-31 |
| 2001 | Priestly ordination of Deacon Bonaventure Unting by Bp Piong, Sook Mission |
| 2002 | Chinese teachers camp BTRC May 30-June 1 |
May 31
| 1976 | Erection of KK Diocese with Bp Fung as diocesan bishop by Paul VI |
| 1983 | 2nd Sabah Catholic Students Camp May 31-June 12 KK Seminary |
| 1996 | World youth day in Tawau |